Cut the pumpkin into 1 - 2 cm pieces. Cut the onion into strips or rings. Put together in a small baking dish, season with salt and pepper and drizzle with 2 - 3 tablespoons of olive oil. Bake on the middle rack for 15 minutes.
Meanwhile, halve or quarter the tomatoes and season with salt. Halve the sheep`s cheese lengthways, i.e. cut into 2 thin slices.
When the 15 minutes are up, spread the tomatoes and sheep`s cheese on the pumpkin and add 1 tablespoon of olive oil. Put in the oven for another 15 minutes.