1. Preheat the oven to 190°C.

2. In a large skillet, heat the olive oil over medium heat.

3. Add the onion and mushrooms and sauté until softened, about 5 minutes.

4. Add the diced tomatoes and cook for another 2 minutes.

5. Crack the eggs into the skillet and scramble until cooked through.

6. Season with salt and pepper to taste.

7. Place the bell pepper halves in a baking dish.

8. Spoon the egg mixture evenly into each pepper half.

9. Sprinkle shredded cheddar cheese on top of each pepper half.

10. Bake in the oven for 20-25 minutes or until the cheese is melted and bubbly.

11. Serve hot and enjoy your delicious keto breakfast stuffed bell peppers!