Heat your oven to 200°C/Fan 190°C/Gas 6. Peel and cut your onion into thick wedges. Halve your tomatoes and cut each half into 4. Place onto a baking tray lined with foil. Drizzle over 1 tbsp olive oil and seasoning. Put to one side.
Peel and grate or crush the garlic clove. Place it into a roasting tin and mix in 1 tbsp oil. Place in the oven for 5 mins to warm the oil. Tip the gnocchi into the tin and toss it in the garlicky oil. Season.
Put the gnocchi in the oven for 25 mins. Place the veg tray on the shelf below the gnocchi and roast for 25 mins too. Toss the veg half way through and give the gnocchi a good shake.
Place half the olives and half the roasted tomatoes in a food processor. Blitz with 2 tbsp water till puréed. This is your tapenade. If you don’t have a food processor, finely chop then mash the olives and tomatoes together.
Take the gnocchi out of the oven. Add the tapenade to the rest of the roasted tomatoes and onions. Toss them all together. Tear the mozzarella and add to the dish. Slide back into the oven for 10 mins to melt the mozzarella.
Remove from the oven and scatter over the remaining olives. Tear over the basil leaves - Add the rocket. Toss everything a few times to mix it. Serve the roast gnocchi and veg in warm bowls with a good grinding of black pepper.