Melt the butter over medium heat in a large frypan. Add the onion and capsicum; cook and stir until the onion is transparent, 5 to 7 minutes. Stir in the mushrooms and bacon, and cook 2 minutes more. Remove the frypan from the hotplate and place the vegetable-bacon mixture in a bowl.
Pour the eggs into the same frypan. Cook and stir gently just until the eggs are soft. Stir the vegetable-bacon mixture into the eggs. Season with salt and pepper. Cook the eggs until firm. Remove the frypan from the hotplate and stir in the tomato and cheese.