Heat oil in a large heavy bottomed pan and sauté cumin seeds, fennel seeds, ginger, garlic, green chillies and onions until lightly browned and fragrant.
Add in the spices, and fry for a few seconds.
Mix in the chopped tomatoes, season with salt, and cook for a few minutes to combine well.
Add in cooked lentils, and water depending on the consistency you like, and let it simmer covered on low heat for 5-6 minutes. This will allow all the flavours to blend in well.
Garnish with fresh cilantro leaves and a squeeze of fresh lemon juice, and serve warm.