Mom and Dad made this along with the Lamb Curry and Raita recipes are also in this book (see pages 141 and 173).
In a medium stockpot, head the mustard seeds over a medium heat until they pop. Add the spices and stir. When the spices are very fragrant (1 min), add the oil and quickly add the onion, garlic and ginger. Stir well and cook for 2-3 min, until soft but not browned. Add the lentils, coconut milk and 3 cups water. Bring to a low simmer, cover and cook for 25 min, stirring occasionally and adding water, 1 cup at a time, to keep the lentils from drying out. (Mom added extra because she cooked it longer.) Stir in the tomato and salt. Cook for another 5 min or so. Stir in the cilantro and serve over basmati rice.