Cook the bacon by frying it in a skillet according to the package directions, or baking it in a 425 degree oven on a wire rack placed over a rimmed baking sheet. Let it cool, and crumble or dice it.
Put the oven rack in the upper third of the oven and preheat it to 450 degrees.
Crack 8 eggs into a medium mixing bowl. Add the whites only for the remaining 2 eggs. Using a whisk, beat the eggs until the yolks and egg whites are thoroughly combined.
Add half the cheese to the egg mixture and stir to combine. Add a pinch of salt and pepper, if desired.
Peel, core, and thinly slice the apples.
In a medium cast-iron or nonstick ovenproof skillet, heat the butter over medium heat.
When it is completely melted, tilt the skillet to coat it with the butter, and add the egg mixture to the skillet. Sprinkle the bacon crumbles evenly over the eggs. [Note: for vegetarian family members, you can leave the bacon off of part of the frittata, use vegetarian bacon, or omit it altogether.]
Gently arrange the apple slices on top of the eggs, in a circular pattern, and sprinkle the remaining cheese on top.
Transfer the skillet to the oven, and bake it until it is firm in the center and the cheese is browned, about 20 minutes.
Remove the skillet from the oven, use a flexible spatula to loosen the frittata from the pan, and carefully slide or flip it onto a cutting board. Allow it to cool for a few minutes before slicing it into wedges and serving.