Steps
1. Preheat your oven to 180°C (350°F).
2. Heat the olive oil in a pan over medium heat and sauté the sliced onions until they are soft and translucent, about 5 minutes.
3. Place the slice of bread on a baking tray and layer it with sautéed onions, followed by the tomato slices.
4. Sprinkle the cheese generously over the tomatoes and onions.
5. Season with salt and pepper to taste.
6. Bake in the preheated oven for 10-12 minutes, or until the cheese is melted and bubbly.
7. Remove from the oven, garnish with fresh basil leaves if desired, and serve hot.