Cook the pasta according to the package directions to “firmâ€. Rinse and place in a large 2-quart casserole dish.
In a medium saucepan over medium heat, melt the butter. Whisk in the flour until combined. Slowly add the milk, whisking non-stop until you have a nice creamy white sauce.
Whisk in the tomato sauce, then add the cheese.
Cook, stirring constantly, until the sauce thickens and all the cheese has melted in approximately 5-6 minutes.
Pour over the macaroni and stir to combine.
Cook uncovered in the oven for 20-25 minutes until the top starts to crisp up.
Remove, cool slightly and serve. This can easily be doubled to feed a crowd or simply to ensure that you have leftovers the next day!