Salt pork may be substituted for the bacon.
Fry bacon slices in 12" skillet until brown and crisp. Set aside on a warm serving platter.
While meat is frying, peel onions, leaving stems to hold for slicing. To prevent your eyes from watering, hold a slice of bread in your teeth while you slice the onions as thin as possible. Discard stems.
Core apples and cut crosswise in circles about 1/4" thick. Apple skins help the slices hold their shape and add color to the dish, so don't peel unless skins are tough or scarred.
Drain all but 1 tb fat from skillet, then add onion slices. Cook over medium-high heat about 3 minutes. Cover with apple slices in an even layer. Sprinkle brown sugar over all, cover skillet, & cook until tender, a few minutes more. Stir only to prevent scorching. Remove to warm plate with bacon slices.
This is a "country" dish, seldom mentioned in cookbooks but recalled by many oldtimers. Some feel sugar is essential; others call it a "sin." If you share Almanzo's enthusiasm you might also like to try fried apples'n'onions with fried potatoes for breakfast sometime.
Here is the recipe Fried Apples'n'Onions from the Little House Cookbook.