Dal Makhani is a traditional Indian recipe for lentils. Most of the ingredients can be found in the International/Ethnic foods aisle of a decent US grocery store but some are harder to find than others. Fenugreek leaves and Ghee (clarified butter) are two such ingredients. Many traditionalists will have you use whole ingredients over the ground/powdered alternatives, but this can make for considerably longer prep and cleaning times. The other downside of using ingredients such as whole cardamom pods, cloves, cinnamon stick etc is the unpleasant surprise of biting into such an ingredient when eating. One compromise is to sachet these ingredients by wrapping them in cheese cloth and tying with food string before blending spices with tomato/lentil mix. Just don't serve the sachet but definitely keep it in the food if you are storing it.
Serve warm with steamed rice or naan.