Preheat oven to 350F and line a baking sheet with parchment paper. Heat oil in a frying pan over medium low. Add diced onion to warm oil and saute until soft and translucent - about 5-7 minutes.

Add ground turkey to a large mixing bowl with the egg, grated parmesan cheese, breadcrumbs, salt, italian seasoning and sauted onions.

Mix everything together until just combined - be careful not to overmix because that will result in tough meatballs.

Using a spoon or cookie scoop, scoop ¼ cup of meatball mixture onto the lined baking sheet. You should have about 10 meatballs total. Using wet hands. Roll the meatballs with damp hands into smooth balls.

Bake at 350F for 20 minutes. Serve with warm marinara sauce.