In a skillet set over medium heat, melt the remaining butter and sauté the chopped onion until translucent, about 3 to 5 minutes. Set aside.
In a large bowl, whisk together the eggs, half-and-half, nutmeg, salt, pepper, hot sauce and cheese. Pour this into the prepared pan. Bake until a knife inserted into the custard comes out clean, about 25 minutes. Remove from oven and place on a wire rack. Allow to stand for about 5 minutes before serving.
Spinach: Add 1 pound chopped fresh spinach to the pan with the onions. (You can skip this step by using 1 cup frozen spinach, thawed and thoroughly drained, no need to sauté.) Stir the spinach into the egg and cheese mixture and continue with the recipe. Serve slices of this quiche on a bed of fresh spinach and orange sections (as shown in the photo).
Denver-style: Add 1/4 cup diced green pepper and 1/2 cup sliced mushrooms to the pan with the onions and sauté until very tender, about3 to 5 minutes. Mix the sautéed vegetables into the eggs, cream and cheese along with1/4 cup chopped cooked ham.
Bacon and onion: In a medium skillet set over medium heat, cook 4 thick slices of bacon until crisp. Drain the bacon on paper towels, chop and set aside. Substitute Swiss cheese for the Cheddar. Stir the bacon with the onions into the cream and egg mixture. Continue with the recipe.