Tortillas are found in every neighborhood bare in Spain, served as tapas, or little appetizers. I sampled dozens when in Seville -- some were eggier than others, some more oniony, but uniformly delicious. Though intended as snack food, with glass of Rioja, and the little dish of terrific olives served gratis, it made a fine light meal.

The dish has only four main ingredients - eggs, onions, potatoes, olive oil, and sometimes thin strips of red sweet pimento - makes dish seem deceptively simple, but it is tricky to make and requires patience. There are many steps, but once you get the hang of it, it's not complex. My first attempt was a mess, because I tried to hurry the process, and did not pay attention  (a lesson in life...).

3 - 4 Tbsp Olive Oil

4-5 Medium potatoes, firm fleshed

1 medium yellow onion

A few roasted red pepper strips, cut thin, if desired

5 large eggs

Salt, and ground black pepper to taste

Use a firm fleshed spud - you do not want to end up with mashed potatoes -- they should be tender, but retain their form. (See photo) I used Yukon Gold this afternoon, but White Rose would do.

Also key is to slice potatoes uniformly - about 1/8" thick. Onion, a little thinner (or they can be chopped - I like the sliced.)

You will need in way of equipment* a big mixing bowl, a sharp knife, and either a non stick or well seasoned 10" frying pan with sloping sides, and a good wide pancake spatula.  Also, a big serving plate larger than pan, lightly rubbed with olive oil. You will be inverting the tortilla on plate later - in manner of upside down cake, but unlike cake, you'll will slide it back into the pan so the other side can brown and cook briefly.

First, slice the onion very thin, then cut onion discs in half.

Peel potatoes, in 1/8" thick slices. Blot them with paper towel to remove excess moisture.

Add two tbsp Olive oil to frying pan at medium high heat until pan is just smoking.

Throw in potatoes and onions, stir and toss so they are all coated with oil (if too dry, add a bit more oil). Spread all evenly in pan, season with salt and pepper, and turn down heat to very low setting. Idea is not to get potatoes crispy, just gently cooked in oil.

Cover pan, and cook for about 20 minutes or until tender -- check at about 15 minutes. ( If you don't have a skillet lid, use heavy duty aluminum foil.)

Meanwhile, break 5 eggs into large mixing bowl, and whisk with fork until just barely blended (do not overbeat).

Dump cooked potatoes and onions from pan into mixing bowl, and toss to coat with egg.

Scrape/Wipe down pan of any sticky bits, and add another tbsp olive oil, again turn to high heat. (Hot pan will help prevent eggs from sticking to to bottom ).

Return potato-egg mixture to pan, arrange potatoes evenly, then turn heat down again. Cook uncovered 20 to 25 minutes or until all egg on top is set. While it's cooking, from time to time loosen sides with spatula edge or knife.

When eggs are set, loosen edges of tortilla a final time, place serving plate over top of pan and invert it (like an upside down cake, thump bottom of pan if it doesn't release). Good mitt potholders are helpful in this operation. An exciting moment in the operation -- you are hoping it will hold together!

Wipe down pan again, then slide tortilla back into it so the uncooked side faces down. Cook two more minutes, turn heat off and let it set about five minutes.

Slice into wedges in the pan, or slide it out again onto serving plate. It's wonderful warm, but nice chilled the next day too. Good picnic food, can be eaten out of hand.

*Special tortilla-making equipment is available: Double sided pans, plates for flipping tortilla, but what you have on hand will work fine.  Below is what perfect tortilla would look like (not mine, alas, it was not so golden brown and slightly uneven -- but quest for perfection is a great deal of the fun)