Prepare the meat "dough". Place the minced meat in a bowl. Chop the onion, add it to the meat along with the cooked rice, soaked breadcrumbs and egg. Mix, add salt and pepper to taste.
Line a baking sheet with parchment paper. Form the meatballs and place them on the pan.
Make the sauce. Mix water with sour cream and mayonnaise. Pour the resulting sauce over the meatballs and bake for 30 minutes.
Place the meatballs on a plate. Enjoy!