Combine meat together with sour cream, mayo, diced onion, salt, pepper, baking powder and 1 cup of breadcrumbs. Mix thoroughly.
Let all mixture sit in the refrigerator for about an hour; this lets all the juices come together.
Using the meat mixture, form small round pieces. Using a large skillet, heat olive oil, over a medium heat. It should be enough to barely cover the bottom of the pan. Fry meatballs in batches, turning them over once during the process. Another great option, is to bake them. Preheat oven to 400F, bake them for about 25 minutes, depending on the size of meatballs.