Ingredients

• 6 ounces penne pasta (2 1/4 cups)
• 1 1/2 teaspoons unsalted butter
• 1 tablespoon virgin olive oil
• 2 tablespoons all-purpose flour
• 2 1/2 cups milk
• 4 1/2 ounces cheddar cheese, cut into 1/2-inch dice (1 cup)
• 3/4 teaspoon salt
• 3/4 teaspoon freshly ground black pepper
• 1 large tomato, (8 ounces), halved, seeded, and the flesh cut into 1/2-inch dice (1 1/4 cups)
• 1 1/2 tablespoons grated Parmesan cheese
• 1/2 teaspoon paprika

Instructions

1. Bring 2 1/2 quarts of water to a boil in a pot. Add the penne, bring the water back to a boil, and boil the pasta over medium heat, uncovered, for about 8 minutes. (The pasta should be al dente, firm to the bite.) Drain the penne in a colander and rinse it under cold tap water until cool, and set aside.
2. Heat the butter and oil in a saucepan, and add the flour. Cook the mixture over medium heat for about 10 seconds, then add the milk, stir it in quickly with a whisk so the mixture doesn't scorch. Bring the mixture to a boil, and boil it for 10 seconds. Add the cheddar cheese, salt and pepper, mix well, then cook over low heat for 3 to 4 minutes. Set aside.
3. When ready to finish the gratin, preheat the oven to 400 degrees.
4. Mix the pasta with the cheddar sauce, and transfer the mixture to a 6-cup gratin dish. Sprinkle the tomato on top of the pasta and sauce. Combine the Parmesan and paprika in a small bowl, and sprinkle the mixture on the pasta. Bake in a 400 degree oven for 30 minutes, until the gratin is bubbly and nicely browned on top. Serve immediately.
5. Note: If making the gratin at the last moment, and assembling it while the sauce and pasta are both hot, do not bake the gratin. Instead, place it under a hot broiler until golden brown on top.