Preheat oven to 375 degrees. Chop onion, break mozzarella cheese into 1-inch pieces and grate pecorino cheese. Set all of that to the side.
Grease a baking dish with non-stick spray. I used olive oil spray, but any works.
Evenly pour the jar of tomato sauce into the dish. Add in fresh / frozen vegetables (including onions) in the dish. Mix.
Add in garlic powder, Italian seasoning, and salt. Mix again.
Pour in broth and mix again.
Sprinkle in half of the pecorino evenly.
Add DRY pasta to the dish and spread out evenly.
Pour water on top. Try to pat down the contents so they are as submerged as possible in the liquid. This helps it cook through properly. Add more salt/seasoning her if you wish, or you can wait until its baked.
Add mozzarella cheese pieces evenly on top. You can do large slices or smaller pieces (as seen in the video). Sprinkle the remaining grated pecorino evenly on top.
Cover the baking dish with aluminum foil. Make sure to fold in on the sides so there are no air pockets.
Bake on the middle rack for 25 minutes. Remove from the oven to "check" the halfway progress. Give it a little mix and press down on any dry noodles sticking out. You want to make sure they get cooked through. Re-cover and bake for another 25 minutes. Remove from oven and serve hot! Don't forget to take note of the cheese pull!!