Dice onions and garlic, fry in oil. Add the spices and tomato paste, let it stew and pour in the lukewarm stock. Add the washed lentils and simmer very gently for approx. 20-30 minutes. Puree with a hand blender or in a blender, adding the sour cream (or yoghurt).
Debark the bread, cut into cubes, fry in herb butter until golden.
Season the soup with salt and pepper. Sprinkle with chopped coriander.