Preheat the oven to 190°C and spray oven dishes or ramekins with low-calorie cooking spray.
Spray a frying pan with low-calorie cooking spray and set on a medium heat. Add the onion and cook for 3-4 minutes, add the mushrooms and fry for a further 3-4 minutes. The onions and mushrooms should be soft and starting to brown.
Divide the sliced sausage, onion and mushrooms evenly between the two dishes.
Spoon the chopped tomatoes over the onions and mushrooms.
Season to taste with salt and pepper and sprinkle over the cheese.
Crack an egg on the top of each one, spray with a little low-calorie cooking spray and season with a little more salt and pepper.
Bake in the oven for 15-20 minutes, until the egg is cooked. Serve and enjoy!