Any grocery store in Spain devotes at least half an aisle to tomate frito, a Mediterranean sauce par excellence. It comes in jars, it comes in briks (cardboard boxes), it comes dried in packets, it comes in any form one could possibly imagine, matched in ubiquitousness perhaps only by American ketchup.
Tomate frito is essentially a slow cooking of tomatoes in a sofrito of the chef's choice. While the packaged version of tomate frito dates only from the 20th century, this puree of 'fried tomatoes' was most certainly being made and used before. Ever since Cortes brought back the first tomato from the Aztecs in the 1500's, it seems likely that cooks combined it with the already popular onion over heat. The first tomato recipes appear in a Naples cookbook in 1692, but the author obtained the recipes from Spanish sources.
Everyone in Spain swears by their mother's (or grandmother's) version, so there are really no definitive rules. I am of the opinion that the simpler the better, otherwise you may as well whip up an Italian tomato sauce. So I keep mine plain-a little onion, salt, and a bit of sugar. Depending on the tomato variety and ripeness, you may not even need sugar. Some people insist on peeling the tomatoes and seeding them, others simply on seeding them, and still others just do a light chop and thrown the tomatoes in, seeds and peels included. I've done it both ways, and as long as you pass it through a food mill, seive, or chinois, I believe it doesn't matter.
As far as uses go, this silky, rich sauce is incredibly versatile. It's featured in typical Spanish dishes, such as tigres (mussels cooked with mirepoix then filled with tomate frito and bechamel before being breaded and fried) and patatas bravas (i love you), as well as infinitely adaptable to any meat or vegetable dish. So hurry-if you live down South you can still grab the last of the season's tomatoes and store some for winter.
5 lbs ripe tomatoes,
small onion, chopped
about 6-8 tbsp oil
tbsp of salt
pinch of sugar
In two 12 inch saucepans, heat oil (enough to cover bottom of pan) over med. high heat. Add half of onion to each pot. Fry until translucent, not browned. Add tomatoes, dividing equally between pots, sprinkle with salt and sugar, and turn heat to low. Cook for 30-50 minutes, until tomatoes are dark red and slightly caramelized.
Blend very well and pass through strainer, pressing to release all the sauce.