Dice the carrots, onions and apple. Sweat onions and carrots in clarified butter for about 2 minutes, sauté the lentils and apple briefly and dust everything with curry powder. Sauté briefly and fill up with the vegetable stock. Cook for about 20 minutes, until the vegetables are soft. Season the soup with salt, pepper, chilli and lemon juice. Stir in yogurt and puree the soup finely.