1. Peel the onions and cut them into thick slices. Cut the tomatoes into thick slices. Grate the cheese and set aside.

2. In a saucepan, cook the onion slices over low heat, with 2 tsp (1 fl oz) of oil and 1/2 cup (4.22 fl oz) of water. Remove from heat, season with salt and pepper.

3. Preheat the oven to 400°F (204°C). In a large quantity of boiling salted water, cook the macaroni al dente. Drain and mix, in a large bowl, with 1 tsp (0.5 fl oz) of oil.

4. Transfer half of the pasta to a greased gratin dish. Cover with half of the onions and olives, then half of the tomato slices. Repeat, finishing with the tomatoes and 2 tsp (1 fl oz) of oil.

5. In a bowl, beat the eggs with the tomato concentrate, milk, a pinch of salt, and pepper. Pour over the tomatoes.

6. Bake for 20 minutes. Remove the dish from the oven, add the grated cheese, and return to the oven for 15 minutes. Serve.