Preheat the oven to 400° F.
In a large mixing bowl, add the ground beef and break up as much as possible with a wooden spoon.
Add in the diced onion, minced garlic, nutritional yeast, bread crumbs, balsamic vinegar, soy sauce, red pepper flakes, olive oil, onion powder, garlic powder, salt, pepper and fresh parsley.
Mix to get all of the ingredient well combined.
Using your hands or a ice cream scoop, shape the mixture into 6 large meatballs or 12 smaller ones.
Bake for 25-30 minutes, until firm and meatballs start to brown.