Macaroni and Cheese with Tomatoes

Preheat a convection oven to 180°C (approximately 350°F). Cook the macaroni in boiling salted water until al dente, then drain and rinse. Peel and finely chop the onion. Cook the onions in the butter, then stir in the flour and sauté briefly. Gradually incorporate the cream and milk, stirring constantly. Simmer for 5 minutes, then stir in half of the cheese. Season to taste with salt, pepper, and cayenne pepper. Rinse and halve the tomatoes. Mix the tomatoes and macaroni, then transfer to a baking dish. Pour in the cream sauce. Top with the remaining cheese. Bake for 25 minutes, or until golden brown.