Steps
1. Preheat the oven to 350°F (180°C).
2. Cut out the center of the bread slice to create a well.
3. In a bowl, mix the egg, diced onion, and chopped tomato.
4. Pour the egg mixture into the bread well.
5. Bake in the oven for 10-15 minutes until the egg is cooked through.
6. Serve warm.