West Indian spiced aubergine curry

Name: West Indian spiced aubergine curry
Prep time: 30 min
Cook time: 15 min
Total time: 45 min
Cuisine: Indian
Ingredients: 1 tsp ground cumin; 1 tsp ground coriander; ½ tsp ground turmeric; 1 large aubergine; 2 tbsp tomato purée; ½ green chilli , finely chopped; 1cm piece ginger , peeled and finely chopped; 2 tsp caster sugar; ½-1 tbsp rapeseed oil; 3 spring onions , chopped; ½ bunch of coriander , shredded; cooked rice , natural yogurt, roti and lime wedges, to serve