Toasted Spices and Onion with Green Lentils (Dhania Jeera Aur Sabud Moong)

Ingredients

1 cup whole green lentils (sabud moong), picked over for stones
2 tablespoons Ghee (clarified butter) or canola oil
1/2 cup finely chopped red onion
1 medium-size tomato, cored and finely chopped
1/4 cup finely chopped fresh cilantro leaves and tender stems
1 1/2 teaspoons coarse kosher or sea salt
1 teaspoon Toasted Cumin-Coriander Blend (see below)
1 teaspoon ground Deggi chiles (see tips) or 1/2 teaspoon cayenne (ground red pepper) mixed with 1/2 teaspoon sweet paprika
1/4 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 may become cloudy. Drain this water. Repeat three or four times, until the water remains relatively clear; drain. Now add 4 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 mostly tender but still firm-looking, 30 minutes.
While the lentils are simmering, heat the ghee in a medium-size skillet over medium-high heat. Add the onion and stir-fry until it is light brown around the edges, 3 to 5 minutes.
Stir the tomato, cilantro, salt, spice blend, chiles, and turmeric into the onion. Cook until the tomato is softened but still slightly firm, 3 to 5 minutes. Remove the skillet from the heat and set it aside until the lentils are ready.
When the lentils are tender, add the tomato sauce. If some of the sauce still adheres to the skillet, pour a scoop of the lentil mixture into the skillet and scrape the bottom to deglaze it, releasing the collected bits of onion, tomato, and spice; add this to the pan. Continue to simmer the dal, uncovered, stirring occasionally, until the sauce thickens, about 15 minutes. Then serve.

If the curry is not acidic enough for you, squeeze in the juice if a medium-sized lime just before you serve it, for that clean, crisp, gusto.
I often cook a batch of whole green lentils, without adding any seasoning, for later use. I refrigerate it for up to 4 days, or freeze it for up to a month, and then I know I have a batch on hand for those days when I don't want to cook dried lentils from scratch. If you happen to have cooked lentils on hand now, by all means use them: Add 1 to 2 cups water to the lentils when you reheat them; this allows the spiced tomato sauce to infuse its seasonings into the curry without drying out the dish. (You will need to add water even if you stored cooked lentils in their cooking liquid, because they have a tendency to absorb any liquid as they stand.)
Ground "Deggi chiles" is a mixture of dried mild red chile varieties, prized for its deep red-orange color and gentle heat. Most of the red color comes from dried red capsicum (bell pepper) and Kashmiri chiles. It is available in boxes (100 grams) under the brand name "MDH," found in any Indian grocery store.