This is a favorite Atkins-friendly recipe. We frequently eat this or sometimes make a Greek version...
Preheat oven to 350 degrees F (175 degrees C).
Heat a large skillet over medium heat. Add bacon and onion; cook and stir until sizzling, about 5 minutes. Add beef; season with salt and pepper. Cook and stir until beef is no longer pink, about 5 minutes. Season with garlic salt and onion powder. Cook until browned, about 5 minutes more. Drain excess grease.
Press beef mixture into the bottom of a 9-inch pie plate. Cover with 3/4 cup shredded Cheddar cheese.
Whisk eggs, mayonnaise, and heavy cream together in a bowl. Pour over Cheddar cheese and beef mixture in the pie plate.
Bake in the preheated oven until set, about 45 minutes. Sprinkle remaining 1/4 cup Cheddar cheese on top. Continue baking until cheese is melted, about 10 minutes.