• 2 tablespoons vegetable oil
• 1 large onion, finely chopped
• 4 garlic cloves, finely chopped
• 1 tablespoon grated fresh ginger
• 1 red chilli, sliced, plus extra to serve
• 2 teaspoons ground cardamom
• 2 teaspoons ground cumin
• 2 teaspoons curry powder
• 2 teaspoon ground turmeric
• 1 tablespoon garam masala
• 400g can chopped tomatoes in juice
• 800g medium firm fish fillets (such as hoki), cut into 3cm cubes
• Coriander leaves, to serve
• 1 small red onion, thinly sliced, to serve