Cook the bacon: Preheat the oven to 400 degrees, and prepare a baking sheet with a baking rack.
Arrange bacon on the rack in a single layer. Bake for 15 to 20 minutes, until crispy.
Make the egg “buns”: On the stovetop, heat a nonstick skillet. Place two, 3-inch Mason jar lids in the skillet and spray with nonstick spray. Crack one egg into each lid. Cover the skillet and cook for 3 to 5 minutes, until the whites are set. Repeat with remaining eggs.
To assemble: Place one egg “bun” on a plate, add 3 slices of bacon, one slice of tomato and one lettuce leaf. Top with remaining egg “bun”, and repeat to make 4 sandwiches.