Simmer the crushed tomatoes, oregano, 1/4 teaspoon garlic powder and 1/4 teaspoon salt for 10 minutes until thick enough to mound on a spoon.
Divide the beef into 8 portions and flatten each into a 5-inch round.
Place one mozzarella piece in the center of 4 rounds, cover with the remaining rounds and pinch the edges firmly closed.
Season with the remaining salt and pepper, then chill the stuffed patties for 10 minutes.
Cook the patties in a skillet over medium heat for 5 to 6 minutes per side until the meat beside the cheese pocket reaches 160°F.
Rest the burgers for 3 minutes while mixing the butter with the remaining garlic powder and spreading it on the buns.
Toast the buns cut-side down, then fill each with one stuffed patty, 1/4 cup tomato sauce and Parmesan.
