Preheat oven to 400°F. Line a baking sheet or square pan with parchment paper; set aside.
Using a medium bowl, combine the bread crumbs and milk; let soak for 5 minutes.
Meanwhile, add the olive oil to a medium frying pan and place over medium-high heat. Once hot, add the diced onions and cook for 6-7 minutes, or until onions begin to soften. (Note: Leave the skillet out as it will be used again once the meatballs are cooked.)
Transfer onions and soaked bread crumbs into a large bowl. Add all of the remaining meatball ingredients (beef, pork, egg, parsley, garlic, salt, pepper, oregano, red pepper and Parmesan cheese). Mix until just combined.
Shape mixture into (12) golf ball-sized meatballs and place 1” apart on the prepared baking sheet.
Bake for 18-22 minutes, or until meatballs are no longer pink in the center.
Reduce oven temperature to 350°F.
Transfer cooked meatballs back into the skillet. Add tomato sauce and Melinda’s pizza sauce, stir until well combined. Cook over medium heat, stirring occasionally, for 8-10 minutes, or until sauce has thickened noticeably. Remove skillet from heat.