crusty bread or mashed potato, to serve (optional)
In a medium pan, heat 1 tbsp of the oil over a medium heat. Add the onion and garlic to the pan and cook for 5 mins. Tip in the tomatoes with a splash of water, increase the heat and allow to bubble for 15 mins.
Meanwhile, in a large bowl, combine the lemon zest, mince, fennel seeds and a good pinch of seasoning. Mix well, then shape into walnut-sized balls.
Heat the remaining oil in a lidded frying pan over a medium heat. Add the meatballs and brown for 5 mins, then pour the tomato sauce into the pan. Simmer for 10 mins, then add the kale, cover with a lid and cook for 5 mins more until wilted. Season to taste, and scatter over the pine nuts. Serve with the lemon wedges, for squeezing over, and crusty bread or mash, if you like.