Sweet Potato Red Lentil and Capsicum Soup

Ingredients

• 1 tablespoon oil
• 1 large onion, diced
• 2 red capsicums, roughly chopped
• 5cm piece fresh ginger, peeled and roughly chopped
• 2 cloves garlic, crushed
• 2 teaspoons whole cumin seeds
• 1 teaspoon turmeric
• pinch dried chilli flakes, plus extra for serving
• salt, to taste
• 500g orange sweet potato, peeled and chopped
• 400g can good quality chopped tomatoes
• 1 cup red lentils
• 6 cups chicken or vegetable stock
• 500ml Greek-style natural yoghurt
• 1/2 cup finely chopped coriander, plus extra for garnish