Fill your kettle and boil it. Fill a large pan with the hot water, topping it up if needed, and add a pinch of salt. Cover and bring the water back to the boil. Meanwhile, peel and finely chop the onion.

Preheat your grill to high. Warm a large frying pan on a medium heat. When warm, add ½ tbsp olive oil, the onion and a pinch of salt and pepper. Fry, stirring, for 5 mins, till the onion has just started to soften and brown.

The water in the pan should be boiling by now. Add the gnocchetti to the pan and simmer for 8 mins, till the pasta is tender but still has a little bite. Meanwhile, quarter the cherry tomatoes.

Stir the cherry tomatoes into the onion. Cook for 3 mins, stirring once or twice, till the tomatoes start to soften. While the tomatoes cook, peel and finely chop or grate the garlic. Finely chop the chilli, scraping out the seeds and white pith for less heat. Rinse the capers under cold water (they can be salty), then roughly chop them.

Stir the garlic, chilli and capers into the tomatoes. Add 100ml water. Cook, stirring every so often, for 5 mins, till the tomatoes are pulpy and have broken down to form a rough sauce. Meanwhile, drain and coarsely grate the mozzarella.

When the pasta is cooked, drain it and stir it into the tomatoes. Taste and add a little salt or pepper if you think it needs it. If your frying pan is ovenproof, scatter the mozzarella over the pasta in the pan and slide it under the grill. Otherwise, transfer to an ovenproof dish, top with the grated mozzarella and slide under the grill. Cook for 2-3 mins till the mozzarella is melted and golden. Let the pasta gratin cool for a few mins before serving.