1. Preheat oven (or toaster oven) to 400°. Split English muffin; toast directly on oven rack. Transfer to a rimmed baking sheet (or toaster-oven tray). Spread muffin halves with butter.
2. Layer bottom half with Canadian bacon, Swiss cheese, and tomato; sprinkle with coarse salt and ground pepper. Return to oven; bake until cheese has melted, about 5 minutes. Top with other muffin half.

Per serving: 368 calories; 18 grams fat; 22.7 grams protein; 30.9 grams carbohydrates; 5 grams fiber

Note: Note: Instead of butter, you can spread the muffins with Dijon or grainy mustard; you can also use other types of cheese, such as provolone or cheddar.