BARCELONA, SPAIN — The ripest tomatoes, plump cloves of garlic, shellfish recently plucked from the sea: Spanish cooks start with excellent ingredients and season them with care, letting the flavors of the food shine through.

Tourists mingle with chefs and local residents at La Boquería, a vast market that is the best introduction to the wonderful foods that Barcelona has to offer. Shoppers cram the narrow aisles, stopping at stalls overflowing with fruit, butcher shops and cheese shops, freshly caught fish arranged on beds of ice, bakeries displaying pastries, candy stores and nut shops. Spice shops offer small tins of saffron. Dozens of varieties of olives are for sale, along with cans and bottles of olive oil.

"You know that we really like olive oil, right, and we use quite a lot," said Teresa Rio, who teaches at Cook & Taste, an English-, French- and Spanish-language cooking school. Her kitchen classroom is perched at the top of three steep flights of stairs in a building on La Rambla, the bustling street in the heart of Barcelona that is also home to La Boquería. (Classes are about $90 per person; complete information is available at cookandtaste.net.)

At a class that my daughter and I attended this summer, Rio orchestrated a meal of cold tomato soup; a Spanish tortilla, which is essentially a potato-onion omelet; seafood paella studded with squid, mussels and shrimp; and crema Catalana, a dessert that's a cross between pudding and crème brulée.

The soup has only three ingredients: tomatoes, balsamic vinegar and a pinch of salt. It's topped with dollops of alioli (the Spanish version of garlic mayonnaise) and parsley pesto. A sprinkling of grated smoked sheep's cheese is the finishing touch.

"If you don't like garlic, lo siento, I'm sorry," Rio said. "Everything has garlic here."

She offered small plates of marinated olives at the class to take the edge off the students' hunger. Marinated olives also are a standard offering at tapas bars, which punctuate almost every block in Barcelona and are another great way to sample the city's flavors.

Some tapas bars give patrons a plate and invite them to help themselves to a variety of tapas, which are bite-size servings sometimes big enough for two to share. Each tapa should be picked up with a toothpick; when it's time to settle the bill, the server counts the number of toothpicks left on the plate. Other restaurants have menus and table service for their tapas.

The tapas themselves can be hot or cold. Tortillas are always on the menu, either the basic potato-onion recipe or versions with other ingredients, perhaps zucchini, shrimp or the Spanish serrano ham.

"We eat tortilla all day," Rio said. "Basically, for breakfast and for dinner."