Washthe lentils under running water to rinse off excess starch.
In a medium saucepan, heat a good splash of olive oil over medium heat. Add the chopped onion and a pinch of salt. Fry until soft and golden.
Add the grated carrot and minced garlic and cook for a few more minutes until softened.
If the mixture looks dry, add another splash of oil. Stir inthe cumin, coriander, and turmeric, and cook for 1–2 minutes until fragrant.
Add the red lentils and stock to the pan along with the ground black lime.
Bring to a gentle boil, then reduce the heat to low. Coverand simmer for 20 minutes, or until the lentils are soft and the soup has thickened. For a smoother texture, blend the soup completely, or blend half and return it to the pan to keep some texture.
Cheese Toastie: While the soup is simmering, prepare the toasties. Butter eight slices of bread, then layer about 50g of cheddar cheese between each pair. Toast in a hot pan or sandwich press until golden brown and the cheese has melted.
To finish the soup: Squeeze in some lemon juice, then taste and season with salt and pepper as needed. In a small pan, melt the butter with cumin and smoked paprika until bubbly. Drizzle over each bowl of soup and serve with a cheddar cheese toastie.