To a large saucepan add the lentils, turmeric and water. Partially cover with a lid and simmer for 15-20 minutes until the lentils are broken down.
While the lentils cook. Add the butter over to a separate pan over medium-low heat. Add the garlic, ginger, cumin, mustard powder, garam masala and tomato. Stir to combine. Cook for 2 minutes stirring. Add the cooked lentils, salt and cilantro, mix well and remove from heat.. Taste for seasoning, add more salt if needed.