"This is one of my family's choice meals. I have even taught my 11-year-old daughter to make it. Awesome for busy weeknights and when you have your kid's friends over. If you prefer it meatier add more bacon."
Cook and stir bacon and onions in a skillet over medium heat until bacon is crisp and onions are softened, 10 to 15 minutes. Add tomatoes to skillet; cook and stir until liquid is evaporated, 5 to 10 minutes.
Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes. Drain and return pasta to pot.
Preheat oven to 355 degrees F (180 degrees C).
Stir 3 cups Cheddar cheese into the tomato mixture until cheese is melted and sauce is thickened, about 5 minutes. Mix sauce into pasta. Pour pasta mixture into a 9x13-inch baking dish and top with remaining Cheddar cheese and mozzarella cheese.
Bake in the preheated oven until cheese is golden brown and crisp, about 15 minutes.