Three apples, peeled, cored and sliced into 16 wedges each
Juice of one lemon
2 tablespoons butter
4 tablespoons sugar (for apples)
Eight cinnamon sugar doughnuts, torn into 2-inch pieces
Five eggs
1 1/2 cups whole milk
1/8 cup sugar (for whisking)
1/4 teaspoon salt
2 tablespoons butter
Baking spray
Preheat the oven to 375F.
Toss the apple wedges with the lemon juice.
Heat the butter over medium heat in a saucepan. Add the apples and the 4 tablespoons of sugar and cook, stirring occasionally, until browned and tender. Deglaze with about 1/8 cup of water, and set aside.
Spray a 9-by-13-inch casserole dish with baking spray.
Arrange about a third of the doughnut pieces in the dish. Top with about half of the apple filling, then cover with another third of the doughnuts. Top with the remaining apple, and finish with the doughnuts.
Whisk together the eggs, milk, 1/8 cup of sugar, and salt, and pour evenly over the top of the casserole. To this point, the casserole can be prepared up to a day in advance and reserved, covered with plastic wrap, in the fridge.
Drizzle the top of the casserole with butter, and bake for 35 to 45 minutes, until browned on top.