Eggs are one of the most basic Spanish ingredients. The tortilla, a one-inch-thick egg pie-like a flat French omelette or a round Italian frittata can be flavored with a variety of ingredients. Traditionally it was taken along to the fields and eaten at lunch by the farm workers. Today, the tortilla can be found in both fancy restaurants and country roadhouses. This one is common in Andalusia and is made sweet by cooking several pounds of onions until they have caramelized and almost melted.
1. Finely chop the onions. Alternately, these can be chopped in the food processor by pulsing several times. In a skillet, heat 6 tablespoon olive oil, add the onions, and stir to combine. Cover and sauté 15 minutes over medium heat. Do not stir. Remove the cover, stir, and reduce the heat to low. Cover and continue to cook until the onion are very soft and golden, stirring occasionally. This will take 1 ¼ hours total, until the onions begin to almost melt. Remove from the heat and cool 10 minutes.
2. Beat the eggs with salt and pepper and add the onions. Let stand 15 minutes. In a 10-inch nonstick skillet, heat the remaining 2 tablespoons of oil unti! it just begins to smoke, 2 minutes. Pour the eggs into the pan and cook over moderate heat, using a spatula to loosen the edges, 10 to 15 minutes. When the tortilla is almost firm, put a plate over the top of the skillet. Invert the plate and skillet. Slide the tortilla back into the skillet, browned side up. Cook briefly until done. It should be slightly juicy inside.
3. Cut into wedges and serve hot or at room temperature.
NOTE: This can be prepared 1 day in advance.
Bring to room temperature before serving.