This recipe is from the 660 Curries cookbook. It is amazing. I used only one chile and it was still hot. This dish was served with rice with yogurt with mustard seeds.
Red Lentils with a Caramel-Sweet Onion Sauce
1 cup skinned split brown lentils (salmon-colored in this form, masor dal)
1 teaspoon cumin seeds
1 teaspoon salt
1/2 teaspoon cardamom seeds from green or white pods
1/2 teaspoon whole cloves
1/2 teaspoon black peppercorns
3 to 4 fresh green Thai, cayenne, or Serrano chiles
1/4 cup Ghee
1 large red onion, cut in half lengthwise and thinly sliced
1 large tomato, cored and finely chopped
1/2 teaspoon ground turmeric
Place the lentils in a medium-size saucepan. Fill the pan halfway with water and rinse the lentils by rubbing them between your fingertips. The water will become cloudy. Drain this water. Repeat three or four times, until the water remains relatively clear; drain. Now add 3 cups water and bring to a boil, uncovered, over medium heat. Skim off and discard any foam that forms on the surface. reduce the heat to medium-low, cover the pan, and simmer, stirring occasionally, until the lentils are tender, 18 to 20 minutes.
While the lentils are cooking, combine the cumin seeds, rock salt, cardamom seeds, cloves, peppercorns, and chiles in a mortar. Pulverize the blend with the pestle, scraping the sides to contain the mixture in the center, to form a gritty, pulpy mass.
Heat the ghee in a large skillet over medium heat. Add the onion and the pulverized spice mixture. Stir once or twice. Then, cover the skillet and cook, stirring occasionally, until the onion turns caramel-brown with a deep purple hue and the spices smell sweet, 20 to 25 minutes. (meanwhile, when the lentils are tender, simply keep them warm, covered over very low heat.
Stir the tomato and the turmeric into the onion mixture and cook, uncovered, until the tomato softens a little, 2 to 4 minutes. (The tomato juices will deglaze the skillet, releasing the browned bits of onion and spices).
Add the onion-tomato mixture to the dal, and stir once or twice. Simmer, uncovered, stirring occasionally, until the flavors mingle, 3 to 5 minutes. Then serve.