Preheat the oven to gas 6, 200°C, fan 180°C. Line a baking tray with nonstick baking paper and place the frozen salmon fillets on top. Spread the chipotle chilli and smoked paprika paste on top of each, then bake for 20-22 mins until cooked through.
Meanwhile, heat the oil in a large, lidded frying pan over a medium-high heat. Add the onion and cauliflower, cover and cook for 5 mins. Stir, re-cover and cook for another 3-5 mins until lightly browned. Add the chickpeas and curry powder, increase the heat to high and cook, uncovered, for 5 mins, stirring frequently, until the onions have turned a deep golden colour and the cauliflower has softened.
Meanwhile, put the spinach in a colander and pour over boiling water to wilt. Drain well, squeezing out any excess moisture; season.
Divide the chickpea mixture and spinach between plates and top with a salmon fillet. Mix the yogurt with ½ tbsp water, some black pepper and lemon juice to taste, then spoon over each salmon fillet. Scatter over a few coriander leaves and serve with the lemon wedges for squeezing over.