Tourists come back from Spain raving about tapas. If you go to a bar and order a drink, you get a free snack. I've been living in Madrid for almost ten years, and I've had a lot of tapas. (The verb is "tapear.") It's an exercise in luck, especially if you get out of touristy areas, because bartenders feel more free to be capricious or to give you food that might mystify foreigners.
A tapa can be anything from a tiny bowl of popcorn to specially prepared hot dishes. Some bars have restaurants attached and the cook doesn't want the dinner leftovers to go to waste, so you could get whatever they need to get rid of, in the quantities they need to move. Many bars give a small freebie but allow customers to order (and pay for) bigger servings.
Tapas I've known include anchovies, deep-fried tiny squids, small sandwiches of all description, sausages, peanuts, homemade hot potato chips, pork rinds, mixed nuts, ham, various kinds of cheese, slices of roasted pig ears, patatas bravas, fried peppers, miscellaneous salads, paella, tuna turnovers, croquets, shrimp, salt cod, tortilla, meatballs, olives, deep-fried beans, and, once, a full roast pork dinner (leftovers, as I said).
A landmark Spanish dish is the tortilla española, a potato omelet, and it tastes good hot or cold, so it's a great tapa. Here's the recipe:
1 pound of potatoes
1 onion (optional)
salt to taste
good quality olive oil
Peel and slice the potatoes. If you're using the onion, which adds both flavor and a nice moist texture to the omelet, slice that, too. Fry them gently in abundant olive oil with a little salt in a frying pan until very soft: soft enough to mash, but not browned. When they're ready, beat the eggs with salt in a large bowl. Scoop the potatoes from the pan and mix with the eggs. If necessary, add more oil to the pan. (This is not a low-fat recipe.) Pour the mixture into the pan and cook over medium to low heat. When it is cooked on one side, turn it over, and return it to the heat to finish cooking.
Turning it over is the tricky step. I have a set of two frying pans made for tortillas that fit together, so I put a little more oil on top of the tortilla, fit on the upper pan, pick the whole thing up, and quickly flip it. I also have a tortilla turner, which resembles a wide, shallow bowl on a stand. (See photo. I bought my tortilla turner in Toledo.) You slip the tortilla into it, cooked side down, then put the frying pan on top, pick it all up (with hot pads), and flip it over. A properly shaped wide bowl or pot lid could work, too.
If you have trouble turning the tortilla, the worst that can happen is you get scrambled eggs and potatoes. In fact, all Spanish cooks wind up with scrambled eggs the first few times they try to make a tortilla. It will still taste great, so it's okay.
You can add a little cooked ham, seafood, green or red pepper, sausage, or other tidbits to the omelet and still be authentic.
A tortilla can be served at any meal except breakfast, because Spaniards don't eat breakfast.
— Sue Burke
Also posted at my website: http://www.sue.burke.name