Easy sweet potato and cod traybake recipe

Name: Easy sweet potato and cod traybake recipe
Ingredients: 2 tbsp. vegetable oil; 1 tsp. mustard seeds; 1 tsp. mild chilli powder; 1 tsp. ground turmeric; 1 tsp. cumin seeds; 1 tsp. ground coriander; 3 tbsp. mild curry spice paste, we used Patak's; 600 g sweet potato, cut into 2cm chunks; 2 red onions, each cut into 8 wedges; 1 medium cauliflower, cut into small florets; 5 tomatoes, quartered; 400 g tin chickpeas; 4 cod fillets, skinless, around 125g each; Fresh coriander, roughly chopped, to serve