Heat the oven to 200C/180C fan/gas 6. Toss the onion, tomatoes, 2 tbsp curry paste, the chickpeas and 200ml water together in a deep 20 x 25cm roasting tin. Roast for 15 mins until the onions are tender and the tomatoes are just bursting.
Stir everything, then season. Brush the remaining curry paste over the salmon fillets and season. Nestle the salmon into the veg in the tin and roast for another 8-10 mins, or until cooked to your liking.
Meanwhile, warm the naan breads – you can do this by putting them directly on the oven rack below the roasting tin. Cut the warmed naan breads into wedges. Swirl the yogurt into the veg in the tin, then serve with the naan wedges for dunking, a few coriander leaves sprinkled over, if you like, and the lemon wedges, if using, for squeezing over.