Heat your oven to 220°C/Fan 200°C/Gas 7. Halve your cherry tomatoes and arrange in a roasting dish. Set on the top shelf. Roast for 20 mins or till a little blackened around the edges, sticky and collapsing a bit.
Set a pan over a high heat. Halve, peel and thinly slice your onions. Add 1 tbsp oil to the pan with the onions and a pinch of salt. Lower the heat. Cook for 5 mins. Thinly slice your chilli. Peel and grate 1 tbsp of the ginger. Add most of the chilli, the grated ginger and a pinch of curry leaves to the pan.
Rinse your lentils. Add to the pan with 500 ml boiling water. Simmer for 30 mins.
Swirl in your roasted tomatoes. Grate in the zest of your lime and a good squeeze of juice.
Heat 1 tbsp oil in a small pan over a high heat. Add the remaining chilli slices and a pinch of salt. Fry till crisp and golden. Spoon over the soup.