Preheat oven to 350 degrees F (175 degrees C). Grease a muffin tin with cooking spray.
Place bacon on a microwave-safe plate; cook in the microwave until slightly browned but still pliable, 2 to 3 minutes.
Melt butter in a small skillet over medium heat. Add onion and garlic; cook and stir until onion is translucent, 3 to 5 minutes.
Whisk eggs, garlic powder, salt, and pepper together in a bowl. Stir in onion and garlic mixture.
Sprinkle a few pieces of bacon in the bottom of each muffin cup. Cover with half of the egg mixture. Add a few more pieces of bacon; top with remaining egg mixture.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 20 to 30 minutes. Sprinkle Cheddar cheese on top.
