It’s midweek in Madrid, around 3 p.m., and my husband and I are finally tucking into lunch at the Mercado de San Miguel. It’s day two of our trip, and the rainy Plaza Mayor is deserted. But here, only a block away, all of Madrid seems to be eating and drinking.

We walk around admiring the Mercado’s ­century-old ironwork structure and stop to sample tapas at one of the 30-plus small vendors. We start with fat green olives, each stuffed with something different — Ibérico ham, manchego cheese and — my favorite — anchovies. Across the aisle, the croquetas oozing Roquefort cheese call my name. We also experiment with some made of bacalao, which is dried salt cod.

This makes us thirsty, and we see that people are hopping from vendor to vendor, picking up tapas and downing it all with glasses of wine or samples of sherry. We buy a crisp white Albariño at Pinkleton & Wine and wander over to Qué Bonito Es Panamá, where the glass countertops literally groan with food.

We slip into a spot next to a Spanish family and watch as sautéed mushrooms with large shrimp arrive, then a small paella and a plate of pimentos, their green skins puckered from roasting. The couple catches us staring as they strip the pimentos with their teeth. They laugh and offer a taste. We order the same thing and eat while standing, our coats on, the roar of the lunchtime crowd all around us. We’re still there at 5 p.m.

We make a vow this trip: We eat only tapas. My husband spent a semester studying in Madrid during the Dark Ages, and our first trip as a couple was to Toledo, Córdoba and Granada 14 years ago. We ate lavishly (and often free) on tapas. Now we’re back to check up on my husband’s daughter, Jaclyn, during her semester abroad. (We had looked at Facebook once too often, and a parental checkup seemed in order.)

In Madrid, we start by working our way around the tapas zone between the Puerta del Sol and Plaza de Santa Ana — quickly realizing that free tapas are endangered. But at Taberna La ­Alhambra, the atmospheric Hemingway haunt, we get chorizo and potato chips (now ubiquitous in Madrid) free with our drinks. And we discover torta de camarones, a thin pancake of smashed-up shrimp (shell and all). Can’t stop stuffing those salty fritters in our mouths.

With Jaclyn in tow one night, we stop at Casa Alberto, one of Madrid’s oldest tabernas, and tapa on veal meatballs and our first really good tortilla de patata, the potatoes nestled in creamy eggs. Jaclyn teaches us something new too: Trust the chef when he experiments. She orders pumpkin ravioli wrapped in zucchini and stuffed with goat cheese. (The brat eats the whole thing.) Afterward, we roll down the hill to Los Gatos, where we wash salmon-and-blue-cheese toasts down with Mahou beer while enjoying the kitschy décor: pictures of Che Guevara, bullfighting outfits and a motorcycle hanging from the ceiling.

Over the trip, we become addicted to the current food fad in Madrid: caramelized onions. We have them on thinly sliced pork on toast (at the oh-so-modern Lateral on Plaza de Santa Ana), on thinly sliced sirloin (at nearby Vinoteca Barbechera) and on goat cheese (at La Casa de las Tostas after a morning of Picasso at the Museo Nacional Centro de Arte Reina Sofía). By the trip’s end, Lateral ranks right after Mercado as our favorite: Its fried artichokes are so light and crisp they make us forget our love affair with torta de camarones.

We succumb to a few real meals. (You can’t keep a 20-year-old walking eight hours a day and doing the museum thing on tapas alone.) We book at Restaurante La Barraca for its old-world service, white tablecloths and heavenly paella. The next day, we wander off into La Latina, the oldest quarter, and discover El Viajero and its upstairs terrace. We dine on pumpkin ravioli (Jaclyn again), veal scallopini in Pedro Ximénez sherry (me) and grilled Churrasco from Uruguay (hubby).

We make only one huge misstep. On our last day, we opt for a languorous lunch at Viña P in Plaza de Santa Ana, ordering from the menú del día like true Madrileños. (Or so we think.) The bean soup with blood sausage is the perfect starter, ­after which the waiter suggests the manitas de cerdo, a local specialty. My husband bites on the offer, but as the waiter leaves, we frantically search our brains for a translation. “Lamb hands,” the waiter cheerfully informs us. Gulp. “Don’t worry, if you don’t like it, I will change it,” he says. Um, OK.

The plate arrives. It is pig’s trotters, hooves with jelly and bits of hair still attached. My husband actually eats half of it. The waiter returns (much later) and admits, “Oh yeah, most people don’t like it.” My darling husband just smiles placidly at me and says, “Oh well, great soup, great bread, great wine, great company.” I knew there was a reason I married him.