Keto Burger Fat Bombs

Preheat oven to 375° and grease a mini muffin tin with cooking spray. In a medium bowl, season beef with garlic powder, salt, and pepper.  Press 1 teaspoon beef evenly into the bottom of each muffin tin cup, completely covering the bottom. Place a piece of butter on top then press 1 teaspoon beef over butter to completely cover.  Place a piece of cheddar on top of meat in each cup then press remaining beef over cheese to completely cover.  Bake until meat is cooked through, about 15 minutes. Let cool slightly.  Carefully, use a metal offset spatula to release each burger from the tin. Serve with lettuce leaves, tomatoes, and mustard.