I made this tonight with things leftover in the fridge, based loosely on guidelines in Marcella Hazan's "Essentials of classic Italian Cooking."
-Caramelize half a large red onion. (Thinly slice it, put in a skillet over very low heat with a tablespoon of olive oil, covered, until well wilted, like 30 minutes, then turn up the heat and stir until it gets browned)
-Fry two strips of bacon
-Grate 1/2c parmiggiano reggiano
-Blanch 10oz. fresh spinach in salted water.
-Mix all of this together with three eggs 1/4t of salt and 1/2t black pepper.
Now you melt 1T butter in a non-stick skillet over low heat. Turn on your broiler. Pour in the mixture and smooth it out. Leave it alone and let it cook about 8 minutes, until it is starting to get set and the sides will lift away from the pan. Take the skillet and put it under the broiler for about 45seconds so that the top can get finished.
That is all. This has much more spinach than you think is correct, but it is healthier like this, not so heavy in the gut, and you will see that it holds together just fine. You can replace parmesan cheese with gruyère, comté, or "swiss." My sources tell me that all of these pair well with spinach.
Serve with champagne, beer or coffee, depending on the occasion and your likes.