Arrange the English muffin halves on a baking sheet. Place an equal amount of baked beans on each muffin half. Layer beans with onion, tomato, cheese, and bacon.
Bake 20 minutes in the preheated oven. Set oven to broil, and continue cooking 1 to 2 minutes, until bacon is crisp. Watch constantly during broiling to make sure bacon does not burn. Serve immediately.