Steps
1. Heat olive oil in a non-stick skillet over medium heat.
2. Add sliced onions and cook until softened, about 5 minutes.
3. Add sliced potatoes and cook until golden brown and tender, about 10 minutes.
4. In a bowl, beat the eggs and season with salt and pepper.
5. Pour the beaten eggs over the cooked onions and potatoes in the skillet.
6. Sprinkle diced tomatoes on top.
7. Cook until the bottom is set and the top is slightly runny, about 5 minutes.
8. Carefully flip the omelette using a spatula or a plate.
9. Cook for another 2-3 minutes until the eggs are fully set.
10. Remove from the heat and let it cool slightly before slicing and serving.