1. Start by making the meatballs. Break the mince into a large bowl, and tip in the breadcrumbs. Halve the chilli, flicking out the seeds and white pith, and finely chop the chilli. Finely grate the lemon zest. Peel the garlic and crush or finely chop. Scoop half the garlic into a bowl and set aside for later. Grate half the parmesan. Slide the chilli, lemon zest, the remaining garlic and the parmesan into the mince and sprinkle in a pinch of salt and pepper. Mix well with your hands till evenly combined, then roll into small meatballs the size of walnuts. Pop on a plate and set aside.
2. Peel the red onions and finely slice them. Pick and finely chop the rosemary leaves. Roughly chop the olives. Trim the courgettes, and use a vegetable peeler to peel them into ribbons. When you get to the seeded middles, finely slice them.
3. Fill a large pan with water and sprinkle in a good pinch of salt. Bring to the boil. Pour 1 tbsp oil into a deep frying pan and warm to a medium-high heat.
4. Add the meatballs to the frying pan and cook for 5 mins, turning every 1-2 mins, till browned all over. Remove from the pan and transfer to a side plate.
5. Drop the spaghetti into thepan of boiling water and cook for 9 mins, till tender with a slight bite.
6. Meanwhile, lower the heat under the empty frying pan to medium and slide in the onions, rosemary, garlic, olives and a pinch of salt and pepper. Cook for 4-5 mins, stirring occasionally, till the onions have softened. Add the meatballs and warm through, for a few mins, stirring from time to time.
7. When the pasta has 1 min remaining, stir the courgette ribbons into the frying pan. Stir to combine with the other ingredients, till slightly wilted.
8. Drain the pasta, keeping half a mug of the cooking water. Transfer the pasta and the reserved pasta water to the frying pan and stir well, till the liquid thickens and coats the pasta. Squeeze in the juice from the zested lemon.
9. Scoop the pasta and meatballs onto warm plates. Grate over the remaining parmesan and scatter over the rocket leaves and serve.