Mash the meat in a bowl with a spoon, then tip in the onion, apple, red pepper and oregano (and seasoning if you want to). Mash again to mix everything together. Now mix well with your hands until the mixture is sticky and divide into 16 smallish balls. Chill in the fridge while you make the sauce. You can make them up to this stage 2 days ahead, or freeze them.
Make the sauce. Soften the onion in a medium saucepan with the oil. Tip in the tomatoes and simmer very gently, uncovered, for about 20 mins. Add the rest of the ingredients except the basil and slow cook for another 15-20 mins. Add the basil and a splash of water from the kettle. Tip the contents of the pan into the food processor and whizz until smooth.
Heat oven to 190C/fan 170C/gas 5. Gently roll the meatballs in flour. Heat a spoonful of oil in an ovenproof non-stick frying pan, wipe out with kitchen paper, then add the meatballs and fry gently and slowly over a low heat for 10 mins, turning them over once with tongs. (You may need to do this in batches if your pan is not very big.) Drain off any excess fat, pour in the sauce and finish off cooking in the oven for 15 mins. Serve with pumpkin mash.