Melt butter in a large skillet over medium heat; add onion, garlic, and ginger. Saute until golden. Stir in turmeric and lentils; cook, stirring occasionally, 1 to 2 minutes.
Stir in broth, and bring to a boil. Cover, reduce heat, and simmer 15 minutes. Stir in salt and garam masala; cover and simmer, stirring occasionally, 15 minutes or until lentils are tender and mixture is thickened. Serve with hot cooked rice.