Heat broiler to high.
Heat skillet over medium heat and cook bacon. While bacon is cooking, mix cheddar cheese, cream cheese, mayonnaise, garlic powder, onion powder, cayenne, and diced pimento in a bowl.
Once bacon is cooked, place one slice of tomato on the bottom muffin and top with bacon and pimento cheese.
Put under broiler for 5 minutes until the cheese starts melting. Take out of broiler and top with the other muffin half.