Put a little oil in a sauce pan and fry the onion gently until soft (about 5 minutes).
Add the green pepper, chilli, garlic and curry powder. Stir and cook for a minute and then add the lentils and sweet potato. Cover with water, bring to the boil and then lower to a simmer. Cover the pan and leave for 20 minutes.
Check the lentils and sweet potato are cooked. Leave for a bit longer if necessary. Stir in the tahini until it dissolves and then serve.
Nutritional information is approximate and a guideline only.