Heat the olive oil in a pan and add the onion and garlic. Saute until the onions become translucent, about 5 minutes. Set aside and let cool to room temperature.
In a large bowl, combine all of the ingredients except for the olive oil (which will be used for frying the meatballs). Use your hands to mix everything together. Really get in there. It is simultaneously gross and fun.
Mold the meat into balls. You can make big balls or small balls, but I find most people prefer bigger balls (in all contexts).
Heat the remaining 3 tbsp of olive oil in a large non-stick pan. When the oil is very hot, add the meatballs (you will probably need to do this in batches).
Cook until brown on the bottom, and then turn the meatballs over and brown the top (2-3 minutes per side).
Remove the meatballs to a paper-towel lined plate to drain any excess oil.
CAREFULLY place the meatballs in a deep saucepan or pot and cover with the tomato sauce. Cook at a simmer for at least 45 minutes.
Serve your turkey meatballs over vegetables, pasta (if you must), or on their own. Delicious and seriously nutritious.