Heat the butter in a large saucepan and saute the onions  (& carrots if you are using them) over low heat until they are light golden–about 5 minutes. Stir in the paprika, cumin, the tomato paste,  and hot pepper flakes; cover and cook for another 5-7b minutes.

Add the lentils and stir everything together so the tomato and the spices combine with the lentils. Add the water/stock and cover and cook till everything is mushy for about 30-40 minutes. OR use a pressure cooker and cook the lentils till they mushy. ( I always use pressure cooker to cook my lentils).

When the lentils are cooked, use a hand blender to blend the soup is to a smooth consistency, or leave it the way it is if you do not want it like a puree. Crumble the mint leaves and add into the soup. Stir and simmer for 2-3 minutes. Remove the soup from the heat. Sprinkle some of the sumac (save the rest to garnish).  Stir to combine.

Ladle into bowls, serving  lemon wedges/or squeeze of lemon juice and some fresh mint leaves (if available) or crushed dried mint.

NOTE: This soup will thicken a lot as it stands. Loosen with some hot water and re heat, if you are not serving immediately.

See more at http://www.ecurry.com/blog/soups-and-salads/soup/turkish-red-lentil-soup-with-sumac/