Spray a large ovenproof casserole dish with cooking spray or lightly brush with olive oil.
Place the first 7 ingredients (tortellini through red onion) in the casserole dish, and lightly stir to combine. Sprinkle the cheese over the top, and bake for 20-25 minutes.
Garnish with fresh basil or Italian seasoning.
Video
Notes
Adapted from Spend with Pennies Frozen tortellini may also be used. If baking straight from frozen, add an additional 10 minutes or so of baking time, until everything is nice and hot.