Preheat your oven to 400°F and lightly spray a deep, high-sided oven-proof pot, skillet, or 9×13-inch baking dish with non-stick spray.

Empty the completely raw, dry box of pasta directly into the base of the pan. Pro Tip: Using a short, sturdy shape like bowties or rotini is crucial here; their ridges catch the sauce and hold up beautifully to an extended oven steam without collapsing into mush.

Pour the entire jar of marinara sauce and 3 cups of warm water straight over the dry pasta. Sprinkle the Italian seasoning evenly across the top. Stir gently to release any trapped air bubbles underneath the dry noodles.

Stir the defrosted meatballs into the liquid. Use your spoon to gently push down, ensuring as much of the dry pasta as possible is entirely submerged beneath the surface of the sauce.

Cover the baking dish tightly with a sheet of heavy-duty aluminum foil, crimping the edges securely around the rim. Crucial: The pasta cooks purely via the steam trapped inside the pan. If your foil seal has gaps, the water will evaporate, leaving you with crunchy, half-raw noodles.

Bake covered for 35 minutes total. For the best texture, quickly slip the foil off at the 18-minute mark, give the casserole a thorough stir to redistribute the starch, and reseal it tightly for the remaining time.

Remove the foil entirely. Blanket the top with the shredded mozzarella and a final dusting of grated Parmesan. Bake uncovered for an additional 10–15 minutes until the mozzarella liquefies into a bubbling golden crust. Let it rest for 10 minutes before serving to let the sauce thicken up perfectly.