Preheat the oven to 350º F.
Bring a large pot of water to a boil. Add 1 tablespoon of the salt to the macaroni and cook until tender but still firm to the bite, 7 to 8 minutes. Drain well.
Heat a large skillet over medium-high heat. Add the beef and onion and cook, stirring, until the beef is well browned. Carefully drain the fat from the skillet and stir in the tomato sauce, the remaining 1 teaspoon of salt, and pepper. Bring to a simmer over a low heat while preparing the remaining ingredients.