Heat the butter in a large saucepan and saute the onions over low heat until they are golden--about 15 minutes. Stir in the paprika, then the lentils and bulgur to coat them in the butter. Add the tomato paste, stock, and hot pepper, bring to a boil, and cook until soft and creamy--about an hour.
When ready to serve, crumble the mint between your palms into the soup. Stir and remove the soup from the heat. Let rest for 10 minutes, then ladle into bowls, serving each with a lemon wedge and a sprinkling of mint leaves (if available) or crushed dried mint.