Fry the onion and bacon. Place a frying pan over medium heat, pour in the oil and add the onion and bacon. Fry until the onion is soft. Turn off the heat, add the paprika and stir.
Make the béchamel sauce. To do this, heat the milk separately. Then put the frying pan or saucepan on the stove, melt the butter, add the flour and fry it for 2-3 minutes over medium heat. Reduce the heat, gradually pour in the hot milk, constantly stirring the sauce. Take the cheddar cheese, setting aside a little for sprinkling, and add it to the sauce. Stir constantly until the cheese melts. Salt and pepper the finished sauce to taste.
Cook the pasta. Pour water into a saucepan, add salt, and put on the fire. After boiling, add a portion of pasta. Cook until done. Then throw the pasta into a colander and let the water drain.
Bake macaroni and cheese with bacon in the oven. Preheat the oven to 200 degrees. In a baking dish, mix all the ingredients: boiled macaroni, bacon with onions and sauce. Stir and sprinkle with Parmesan cheese and the remaining cheddar cheese. Put in the oven and bake until golden brown.