By Paul Reidinger

EVERY RESTAURANT SHOULD have a signature dish – a distinctive preparation, permanently fixed on the menu, that customers will associate with the place and order over and over again. It goes without saying (and therefore let me say it) that the dish should be not just interesting but good.

The best signature dishes in these parts tend not to be fancy. One thinks of the roast herbed chicken at Zuni Café and the shrimp-and-scallop potstickers at Firefly. To this august but unassuming list we can now add the tortilla soup at Café La Taza, a six-year-old coffee house, on a fairly scruffy stretch of Mission Street, that recently began serving dinner.

The soup (which, at $7, is not cheap, though you get a quite large bowl) is a pale pinkish color, like tomato pulp. Apparently tomatoes are involved, along with milk and cream, but beyond those vague revelations our smiling server would not venture. In the middle of the bowl rises a low island of crisp tortilla strips – it looks as if beavers have been hard at work – while dribbled across the surface of the soup are streaks of lime crème fraîche. The soup does not look addictive, but it is, as one notices after a spoonful or two and finds oneself unable to set the spoon down.

The perils of dinner service along Café La Taza's run of Mission are palpable. Just a few doors away stands the handsome but empty Art Deco hulk of Mission Bar and Grill, which offered a menu of Middle Eastern, Mexican, and all-American dishes and lasted less than a year. Not far the other way is Bruno's, a shape-shifter that has morphed from dot-com temple to high-end Italian spot to discount pasta house. But ... no tortilla soup with lime crème fraîche at those places.

The dinnertime chef, Jerry Mendoza, cooked at Joanna Karlinsky's Meeting House in Pacific Heights (since become Quince, with new ownership), and while his presentations at La Taza don't quite rise to that level, they are imaginative and vivid – and quite a bit less expensive. The kitchen strikes an attractive note right off by presenting, instead of a basket of bread, a pile of oven-fried yucca sticks, lightly but definitely salted and well suited to dipping in an accompanying ramekin of chipotle mayonnaise. We went through one pile, then another, as if we were devouring another distinctive staple of Mexican, and Mexican-influenced, restaurants: chips and salsa.

Although I grew up in fear and loathing of liver – which always meant calves' liver – I have made my peace with chicken liver, which in addition to being nonmammalian is far less strident on the tongue. Mendoza grills chicken livers on skewers ($5) and serves them with quarters of roasted Yukon Gold potatoes and a glistening, seaweed-like heap of balsamic onion confit, whose slightly fruity bite helps cut the richness of the livers.

That dish is pretty Franco-Cal. More in the nuevo Latino spirit are a pair of fish offerings. One of these is grilled salmon ($11), a large filet that lounges on a bed of avocado halves, sliced and splayed into fans, with a heap of parsley-fried potato cubes on the side. The sauce is tequila-lime cream, which sounds like the sort of thing that could easily be transformed into a $9 drink with the addition of some sugar. Then there is a plate of catfish ($12); the firm, mild filet is breaded and sautéed before being plated, or dunked, in a crock of white bean stew. This reminds me for some reason of pozole: a similar consistency and vivid seasoning.

Desserts suggest a shift in the direction of all-Americanism: coconut-cream pie ($6), say, or chocolate-bourbon bread pudding ($6), with a large globe of ice cream nearby – coffee ice cream, of course, since La Taza remains, despite its handsome eveningwear, a coffee house.

The all-American theme is strongest while the sun shines. The lunch menu offers a familiar range of sandwiches, among them a hefty tuna melt ($6.50), with plenty of fish and bright orange cheddar cheese but too little salt. The accompanying fries are undersalted too, though well crisped and creamy inside. Better is a BLT with avocado, or, in La Taza-speak, a BLTA ($6.25). I love avocado and welcome its sumptuous butteriness here, but what really makes the sandwich are the thick slices of meaty bacon, properly fried to a tender crunch.