Sweet potato lentil curry

Ingredients

• 1 sweet potato
• 100 ml red lentils
• 2 stalks spring onion
• 400 ml tomato purée (passata)
• 200 ml coconut milk
• 1 onion
• 2 cloves garlic
• 1 tbsp ginger (minced)
• 2 tbsp curry powder
• 1 tbsp ground coriander
• 1/2 tbsp ground cumin
• 1/2 cinnamon stick
• 1/2 tsp cayenne pepper
• 1 tsp salt
• 1/2 tsp black pepper
• 2 tbsp canola oil
• 1/2 bell pepper