Preheat oven to broil and place a rack on the upper rack of the oven.
Combine ground turkey, parsley, Parmesan cheese, panko bread crumbs, egg, salt, garlic powder, and red pepper flakes in a bowl.
Gently pack the meat into 8 to 10 meatballs. Gently, because if you handle it too roughly or pack to tightly, you’ll have tough meatballs!
Spray meatballs all over with cooking spray and arrange in a single layer in a 9 or 10 inch ovenproof pan or skillet (this can be a rectangular Pyrex or a nonstick skillet – it doesn’t matter as long as it’s ovenproof!).
Broil meatballs for 3 to 5 minutes or until golden brown on top.
Remove pan from the oven and reduce heat to 400°F.
Pour marinara sauce around the meatballs. Arrange mozzarella cheese over top. Return pan to oven and cook until cheese is lightly browned and a thermometer inserted near the center of a meatball reads at least 165°F, 10 to 15 minutes.