2 T. butter or olive oil
3 large onions, about 2 lbs, quartered and sliced thinly
salt and pepper
3 garlic cloves, finely chopped
8 eggs
1 oz. hard cheese, grated, about 1/3 c.
1 T chopped fresh sage
3 oz. mild creamy goat cheese, crumbled
3 T. reduced balsamic vinegar (optional)

1. Preheat oven to 325F.  Heat 1 T. butter or oil in a large, heavy skillet; add the onions, 1/2 t. salt, and 1/8 t. pepper.  Saute the onions over medium heat for about 10 minutes to release their juices.  Add the garlic; continue to cook over medium heat for about 40 minutes, gently scraping the pan with a wooden spoon to keep the onions from sticking as they caramelize.  (Add a little water if needed to loosen the sugars from the pan.)  Transfer the onions to a bowl and set aside.

2. Beat the eggs in a medium-sized bowl.  Stir in the onions along with the hard cheese and sage.  In a 9 inch saute pan with an ovenproof handle (I use a cast iron skillet), heat the remaining butter/oil to just below the smoking point.  Swirl the oil/butter around the sides of the pan to coat it.  Turn the heat down to low, then immediately pour the fritatta mixture into the pan.  The eggs will sizzle from the heat.  Crumble in the goat cheese and cook over low heat for 5 minutes, until the sides begin to set; transfer to the oven and bake, uncovered, for 20-25 minutes, until the fritatta is golden and firm.

3. :Loosen the fritatta gently with a rubber spatual; the bottom will tend to stick to the bottom of the pan.  Place a plate over the plan, flip it over, and turn thr fritatta out.  Brush the bottom and sides with the reduced balsamic vinegar and cut into wedges.  Serve warm or at room temperature.