Cook the pasta according to the directions on the package. Drain, then set aside.

In a saucepan over medium heat, melt the butter, then sauté the onion and tomatoes for five minutes. Adding flour and cooking for one  min. Gradually pour in the lobster broth, stirring to avoid lumps forming. Bring to a boil to thicken the sauce. Season, then set aside.

Preheat the oven to three hundred fifty °F and place the rack in the middle.

In a gratin dish, combine layers of sauce, macaroni, Swiss cheese and lobster meat. Finish with mozzarella cheese, then sprinkle with breadcrumbs and paprika.

Bake for thirty  minutes, then finish cooking under the broiler to brown the cheese.