Spaghetti Squash Gratin

1 medium spaghetti squash 2 tablespoons butter 1 small yellow onion , cut in half and very thinly sliced 1/4 teaspoon red pepper flakes (or more) 1 teaspoon[...]

1 -2 1/2 lb spaghetti squash 9 fresh sage leaves , 6 of the leaves finely chopped 1 garlic clove , minced and crushed to a paste 2 1/2 cups gruyere cheese ,[...]

1 large spaghetti squash 3/4 cup milk 2 eggs , beaten 2 tablespoons gruyere cheese , grated 1/2 teaspoon salt 1/4 teaspoon pepper 1/4 teaspoon nutmeg 3[...]