Preheat the oven in good time to 200 ° C (convection: 180 ° C).
Brush the bottom of a flat baking dish with oil. Layer alternately with baguette slices, tomatoes, leek and mozzarella. Drizzle with oil, season with salt and pepper.
Bake in the preheated oven on the middle rack for 15-20 minutes until the cheese has melted.
Everything that has been fried, including fried fish, tastes good with it.