FOR THE SWEET AND SOUR SAUCE:2 tbsp. canola oil1 medium yellow onion, minced1 15-oz. can tomato sauce the juice of 1 lemon (about 2 tbsp.)¼ cup firmly packed dark brown sugarKosher salt and freshly ground black pepper, to tasteFOR THE MEATBALLS:2 lb. ground beef chuck2 eggs, beaten⅓ cup long-grain white rice, parboiled for 3 minutes1…