Sweat the finely chopped onion in oil until translucent, add the red lentils. Fry briefly, then deglaze with the coconut milk. Stick with it and, if necessary, add a little more water. Season with curry, salt, pepper and turmeric.
Cook for about 10 to 15 minutes, shortly before the end, add the lemon juice, the finely chopped chilli pepper, the chopped leek and the diced apple and let everything simmer for a few more minutes on a low flame.