01 -
Preheat the oven to 375°F and position the rack in the upper third.
02 -
Bring a large pot of salted water to a boil. Add rigatoni and cook two minutes less than package instructions. Drain and return pasta to the pot; set aside.
03 -
In a skillet over medium-high heat, cook the Italian sausage with chopped onion for about 10 minutes, breaking the meat apart and stirring occasionally until cooked through.
04 -
Stir in minced garlic and red pepper flakes into the sausage mixture and cook for an additional minute.
05 -
Add marinara sauce to the skillet with sausage mixture and heat through for a few minutes.
06 -
Add half of the sausage and sauce mixture to the cooked rigatoni in the pot and gently stir to combine.
07 -
Transfer the pasta mixture into a 9x13 inch baking dish evenly. Dollop ricotta cheese over the top, then sprinkle evenly with Parmesan cheese.
08 -
Spoon the remaining sausage and marinara mixture evenly over the cheese layer, then cover with shredded mozzarella and cheddar cheese.
09 -
Bake uncovered for 20 minutes. Then broil for a few minutes until the cheese is golden and bubbly, watching carefully to prevent burning.
10 -
Let the dish rest for 5 minutes before serving to allow flavors to settle.