In a small dish, combine the cumin, kala jeera, turmeric, cayenne, 1 ½ teaspoons salt, garlic, and ginger. In a small frying pan over medium-high heat, melt the butter and cook until the frothing subsides and the butter has browned slightly. Add the spice mixture and sauté for 20 seconds or so. Stir into the dal. Bring the dal to a simmer, remove from the heat, and stir in the 2 tablespoons lemon juice. Taste for seasoning, and add more lemon or salt as needed. Serve garnished with cilantro, if desired.