Preheat oven to 350 degrees F.
Form meatball mixture into 2.5oz balls, using a kitchen scale.
Add 1 Tablespoon of oil to cast iron skillet and warm to medium heat. One by one, add the meatballs and cook on each side for about 2-3 minutes until outside of meatball is nice and toasty.
Then, place entire cast iron pan in oven and cook for 15-20 minutes, until meatballs have an internal temperature of 165 degrees F.
While the meatballs are in the oven, prepare your veggies and sauce.
Add 1 Tablespoon to pan and saute sliced onions and peppers for about 10-12 minutes, until desired caramelization.
In a small saucepan, warm pizza sauce, careful that it doesn't "pop" all over your stove.
Remove meatballs from oven and create your sandwich!
Layer sauce, peppers and onions, meatballs and top with white cheddar cheese. Lay sandwiches on a cookie sheet, place in oven and broil for 2-3 minutes to melt the cheese.
Remove from oven and enjoy!