In a medium sized skillet, preferably nonstick or well seasoned carbon steel, sauté the onions in olive oil over very gentle heat with a good pinch of salt and a good grind of black pepper until they are very soft and well reduced. This should take about 15 minutes or so. Add spoonful or two of water from time to time to help soften the onions and prevent them browning.

When the onions are nice and soft, turn up the heat and let any liquid cook off. If you want, you can keep going and brown them a bit.

Transfer the onions to a bowl to cool.

Meanwhile, beat the eggs in a separate bowl. When the onions have cooled, add them to the eggs and mix thoroughly. Season the eggs lightly with salt and pepper, bearing in mind that the onions are already seasoned. If using, add the grated cheese and/or minced herbs.

In the same skillet you used for the onion, add a generous pour of olive oil. Heat it over a lively flame until it shimmers.

Then pour in the egg and onion mixture. The eggs should start to "boil" on contact with the oil.

Stir the egg mixture gently, all the while shaking the pan so that as some of the eggs set, the remaining raw egg comes in contact with the hot skillet so it has a chance to set, too.

Then stop stirring and lower the heat a bit. Let the eggs brown well on the bottom. (Use a spatula to peek underneath and check.)

When the bottom of the eggs has browned nicely and the egg has set other than a thin top layer, slip the half-cooked frittata on to a plate. Take another plate of equal size and, holding the two plates together, flip them over.

Add a drizzle of olive oil to the skillet, then slide your half cooked frittata back into the skillet, raw side down. Let the bottom side brown nicely as well.

Serve your frittata di cipolle still hot, warm or room temperature, as you prefer.