Beef meatball with tomato sauce

|Beef meatball with tomato sauce|1 tbsp coconut oil or cooking oil|1 onion, finely chopped|One head of garlic, minced|400g beef mince|1 medium free-range egg|Handful plain flour, for dusting (optional)|1 tsp ground cumin|1tsp brown sugar|1tsp salt|400g can chopped tomatoes|1 tbsp tomato purée