2 teaspoons whole cumin seeds
2 teaspoons whole mustard seeds
1 teaspoon whole fennel seeds
2 cups split red lentils, rinsed
5 cups water
1 (15-ounce) can diced tomatoes
1 medium onion, diced
1-inch piece fresh ginger, peeled and finely grated
1 tablespoon ground turmeric
1 bay leaf
1 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
Fresh cilantro leaves, for serving (optional)
Jasmine rice, for serving
Add the cumin, mustard, and fennel seeds to a small sauté pan, and place on the stove over low heat. Toast the seeds, using a wooden spoon to stir frequently, until fragrant, 3 to 4 minutes.
Add the toasted spices, lentils, water, tomatoes, onion, ginger, turmeric, salt, and pepper in the bowl of a 6-quart slow cooker. Stir together. Cover the slow cooker with the lid, then set to low and cook for 4 to 6 hours, or high and cook for 2 to 3 hours, until most of the liquid has been absorbed and the lentils are soft. Stir before serving.