Carrot puree with lentils and cheese

25 g peeled and finely chopped onion
1/2 tbsp vegetable oil
25 g red lentils
200 g carrots, peeled and sliced
15 g unsalted butter
2 tomatoes, skinned, de-seeded and roughly chopped
50 g cheddar cheese, grated

1. In a saucepan, saute the onion in the vegetable oil until softened (3 to 4 minutes). Rinse the lentils and drain and add to the onion. Add the carrots and pour over enough boiling water to cover generously.
2. Bring to the boil, then cover the saucepan and cook over a medium heat for 25 minutes. Melt the butter in a saucepan and saute the tomatoes until mushy, then stir in the cheddar cheese.
3. Drain the carrot and lentil mixture and reserve the cooking liquid. Combine the carrots and lentils together with 125 ml of the cooking liquid and the tomato and cheese mixture in a food processor and puree to a smooth consistency.