8 ounces mozzarella cheese, cut into 1/2 inch cubes
1/4 cup grated Parmesan cheese
Preheat oven to 400 degrees F (200 degrees C).
Fill a large pot with lightly salted water, bring to a rolling boil over high heat. Stir in the bow tie pasta and return to a boil. Boil pasta, stirring occasionally, until cooked through but still firm to the bite, about 12 minutes. Drain well.
Cook and stir ground beef and onion in a large skillet until beef is no longer pink, about 5 minutes. Drain fat. Stir in pasta sauce and bring to a boil. Reduce heat to simmer.
Stir cooked pasta and half of the mozzarella cheese into the sauce; toss to combine. Transfer to a 2-quart baking dish. Top with remaining mozzarella and Parmesan cheese.
Bake in preheated oven until lightly browned and bubbly, 15 to 20 minutes.