Preheat the oven to gas 4, 180°C, fan 160°C and place the mini meatballs on a baking tray in the centre of the oven. Cook for 10 minutes.
Meanwhile, heat the oil in a medium pan, add the diced onion and fry for 1 minute. Add the kidney beans and chopped tomatoes, and heat through for 6 minutes. Remove from the heat.
By this time the meatballs will be ready, so transfer them into the pan and stir thoroughly to coat them with sauce.
Serve alongside the rice, reheated according to pack instructions.
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For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.