Roast red lentils in a pot for 4-5 minutes while stirring continuously. Place in a sieve and rinse. Return to the pot. Add approx. 900 ml water, bay leaf, butter and 1 1/2 tsp. salt and bring to the boil.
Cover the lentils and cook over medium heat for about 30 minutes.
In the meantime peel and finely dice the onion. Wash and chop the tomatoes. Peel and finely chop the ginger. Heat the ghee in a pot. Brown the mustard seeds briefly in it. Add ginger, chilli, turmeric, cumin and coriander.
Roast for about 30 seconds while stirring. Add the tomatoes and fry for 1-2 minutes.
Add the tomato mix to the lentils after about 20 minutes cooking time and finish cooking. Season to taste with lemon juice. Long grain rice tastes good with it.
Making ghee: Melt butter slowly over low heat. Skim off rising foam. After about 30 minutes no more foam will rise. Pour ghee into a screw-top jar and let it cool down. Close it and store in a cool place.
Ghee can be kept for several months. You can also use clarified butter instead.