Tesoro (teh-SOH-row), Spanish for "treasure," is a family operation run by the brother-and-sister team of Rosie and Ricardo Vera, with help from their parents and siblings. Open since November, it quickly gained a reputation as a hip downtown spot to try nuevo wave-o Mexican cuisine.

Some of the restaurant's éclat stems from its three levels of sharp, colorful decor. Underground, there's the windowless Marin Lounge bar, with DJs Wednesday through Saturday evenings, starting at 9 p.m. The minimalist street-level dining room has original brick walls, a tiny bar, and cowhide banquettes; during our visits, a large plasma screen at one end of the room (next to a platform where a singer-guitarist performs on Friday evenings) silently played geometric designs. The fancier main dining room, one floor up, boasts wrought-iron railings, gilded mirrors, hardwood floors, crystal fixtures, and more brick. Servers run drinks between the street level and mezzanine but still manage to maintain an attitude of warm enthusiasm.

The menu is divided between traditional, regional dishes and creations that exemplify "Mexican food with a French twist" -- a mode of upscale Mexican cuisine that developed at restaurants in the plush Polanco suburb of Mexico City. The chef hails from a longtime Acapulco restaurant family; his style incorporates flavors from the resort cuisine of his hometown. Along with a delightful wine list, beverages include an excellent "traditional" margarita (delicious when made with reposada tequila) and a pleasing house-made sangria. There are also adventurous beer cocktails, such as a salt-rimmed "Michelada roja," made with clams, Clamato, V-8, and lemon juice.

Dinner begins with an amuse-bouche of the chef's choosing, which changes nightly, a sign of serious intentions. These tidbits are sometimes the evening's best bites. We especially enjoyed a tiny, sparkling mound of lime-marinated Alaskan halibut ceviche, dotted with tomato and served on shreds of irresistible house-made tortillas with cilantro cream and dots of chile oil.

Among the appetizers, one standout is tarta de rajas, strips of poblano chile and gooey Oaxaca cheese in cream, layered like a Napoleon on house-made puff pastry sheets. We also loved panuchos de cochinita, a savory small tortilla topped with black-bean purée, then a second tortilla heaped with shredded pork in achiote sauce and pickled red onion shreds with a touch of oregano. This is a great, folkloric dish -- a glorified version of a delectable snack (sold by niños) I once relished on a bus crossing the Yúcatan.

Quesadillas de flor de calabeza, half-moon-shaped tortilla turnovers, are fried until puffed and semi-crisp. Stuffed with mild Mexican cheese and squash blossoms, the cheese (as usual) overwhelms the flowers. The revisionist house ceviche was more of an oddity. It looks alluring, piled high in a martini glass, but it violated both our expectations and tastes, centering on large shrimps and fine little scallops in a marinade that has more lemon than lime. In place of the traditional crunchy (and easily avoidable) minced hot chiles mixed into the seafood, the cocktail is topped with a too-generous splash of chile oil, which tasted harsh and overbearing in context. I love spicy food, but only if the piquancy is proportional to the other flavors.

Fiercer yet, if in a different way, was the baby spinach salad with golden beets, bacon, and green onions in a jamaica (hibiscus flower) vinaigrette. The dressing, simultaneously sweet and citrus-sour, blotted out everything but the beets.

Entrées come in generous portions, but Tesoro has adapted a bad practice from high-end steakhouses -- and adapted it badly. In many of the dishes, the protein and its sauce arrive ungarnished by any starch or vegetable. Unlike steakhouse fare, the flavors of most entrées here are exotic and, in some instances, highly spiced. Your taste buds need relief. Instead, you don't even get a complimentary basket of tortillas. I asked the chef about this later; he said that he prefers to serve many entrées totally ungarnished, so that nothing will interfere with their complex flavors -- an attitude probably acquired from his Acapulco resort-restaurant upbringing.

Taquería-style accompaniments of tortillas, rice, and beans may seem too pedestrian for a restaurant with Tesoro's ambitions, but these constitute the entire list of optional side dishes. It's not the extra six bucks I mind so much as the poverty of possibilities. Steak with hibiscus-flower sauce or halibut with pineapple -- and refried black beans? The beans are luscious, but here, they're the wrong stuff. Rice or tortillas might help, but I craved a vegetable to contrast with these tangy-sweet mixtures -- something chosen by the chef to enhance the other flavors. It's not as if Mexico is a veggie-free zone. Any good Mexican cookbook includes a panoply of vegetable recipes; meanwhile, the bins at the Latino produce market in my neighborhood are heaped with avocados, verdulaga (purslane), and nopales (peeled cactus pads), any of which would be appropriate sides.

The Choice-grade filet mignon with hibiscus (filete a la jamaica) is otherwise terrific. Our tender beef arrived rare as ordered and tasted meaty for such a wimpy cut. The dried flowers in a sweet glaze -- a reduction based on port wine -- swell out like rehydrated fruit, enhancing the faint floral flavor with a hint of licorice.

A credible version of chicken in black Oaxaca-style mole is served with the required underlayer of red Mexican rice. The exciting sauce is less chocolatey than the more common mole poblano (from the neighboring state of Puebla), its color and primary flavors derived from the puréed dark chiles and ground peanuts. A fruity, acidic undertone and a lash of spice kick in after swallowing. The portion consists of a dry breast and a moist leg-thigh piece, scattered with sesame seeds.

Halibut with pineapple (lenguado con piña) offers gently cooked fish slices arranged on overlapping slices of fresh pineapple (strangely dry, perhaps from the heat) set atop a thicker, juicy round of grilled fruit. Everything is bathed with a brick-orange sauce of achiote and nippy chile guajillo -- a pure, puréed chile sauce, reminiscent of the fabulous tomatoless enchilada sauces of New Mexico.

Our chile en nogada, however, was horrible. The traditional recipe calls for room-temperature, meat-stuffed poblano peppers, swathed in a ground walnut-cream sauce, with pomegranate seeds sprinkled on top. This dish (from Puebla) is served for Mexican Independence Day in September, when all the ingredients are in season. I'm happy to encounter it any time of the year, but not in Tesoro's rendition. In the best versions I've had, the chiles were filled with shredded braised beef garnished with fruits, herbs, and spices. Tesoro uses lean, dry hamburger meat, which tastes as if it's been boiled in water and drained to remove all fat, then minimally amended with minced onions and raisins. The final blow is the substitution of harsher and hotter chiles pasillas for gentle poblanos. Chef Martinez later verified that he prefers the pasillas, to counter the sweet flavors of the filling and toppings. (Well, some like it hot.) Officially, the chef includes both ground walnuts and pine nuts in the cream sauce, but we couldn't perceive any nuts. It tasted like chiles no-nogada, and that's no good-a.

Our coffee was weak and served tepid; the desserts were simple and sparing of effort. A pastel de crepas ("crêpe cake") had layers of "chocolate crepes" alternating with chocolate whipped cream, piled atop a pool of raspberry sauce. Not too sweet or chocolatey, the effect was pleasant, although the crêpes had a texture closer to tortillas than their French namesakes. Simpler yet are plátanos machos, ripe plantain slices robed in caramel sauce. Plantains have a starchy texture, so this dish won't be to all tastes. (I'd prefer regular bananas, myself.) In summer, I might go for the Michoacán-style Mexican popsicles in tropical flavors. The final dessert choice is the inevitable flan, which I didn't try.

With Tesoro, the Gaslamp is now home to three restaurants-with-attached-nightclubs serving alta cocina mexicana (Mexican haute cuisine) -- the Latin Room and Candelas are the other two. Tesoro is promising, and many dishes are delicious. Overall, though, it still can't hold a candle to Candelas, the oldest and best of the trio (if also the priciest), where every dish comes complete with all its necessary parts.

ABOUT THE OWNERS AND THE CHEF

Rosie Vera, the primary force behind Tesoro, was raised in San Diego. Her mother is from Zacatecas, her father from Michoacán. "The restaurant has been a long time in the planning," she says. "I grew up in the kitchen with my mom and grandma. I was fascinated by the cooking. So I always wanted to open a Mexican restaurant and serve the authentic dishes that we serve here -- with the modern twist, of course. I didn't want to do the traditional presentation, so we added a little French twist to it, which is very good."

She started saving for her own restaurant back in high school, working two jobs at a time. There was a two-year delay in construction of the restaurant, hassling with the permit process. "I couldn't have gone this far without the support of my family -- my mother, who often does prep in the kitchen, and my brother Ricky, who comes to our rescue whenever and wherever we need him. He's washing dishes right now."

Tesoro's opening chef, Hawaiian-reared David Salgado, moved back to his home state sometime in February, leaving former sous-chef Fernando Martinez in charge of cooking the menu both chefs devised in concert with the owners.

"My family in Acapulco has a couple of restaurants there," says chef Fernando. "They've been cooking for the last fifty, seventy years. They cooked for the governors of the Guerrero state of Mexico. That's how I discovered myself in the kitchen. They taught me how to cook and all about Mexican food." Seven years ago, his father moved to Southern California. "I visited him, and I decided to stay for a little while.

"I have a number of dishes on the menu that are my own recipes. Pollo en tequila [chicken with tequila and tamarind sauce] is my recipe, and so is shrimp and chipotle chiles with creamy rice. The filete mignon al chipotle [filet with chipotles] is from my family, and so is halibut with almonds. I have a lot of my home plates that I want to show to everyone."