1 cup red lentils
4 Tablespoons vegetable oil
1/2 cup finely chopped onion
2 teaspoons grated fresh ginger
2 cloves garlic, chopped
1 fresh serrano chile, stemmed, seeded, and chopped
2 1/2 cups chicken stock, canned broth, or water
1 1/2 Tablespoons fresh lemon juice, or more to taste
salt to taste
1/2 teaspoon garam masala
1/2 teaspoon ground ginger
1/2 teaspoon ground cayenne pepper
1/2 teaspoon ground cumin
1 teaspoon yellow mustard seeds

1. Pick over the lentils. Place in a colander and rinse under cold running water. Place in a bowl, covered with cold water, and soak for 30 minutes.
2. Drain. Heat 2 tablespoons oil in a heavy saucepan over medium-low heat. Add the onion, ginger, garlic and chile and cook until the lentils and stock and bring to a boil. Skim if necessary.
3. Reduce the heat to low, add the lemon juice and salt, and simmer, partially covered, until the lentils are tender, 25-30 minutes.
4. Heat the remaining oil in a small skillet over low heat. Add the garam masala, ground ginger, cayenne, cumin, and mustard seeds and cover.
5. Holding onto the lid, shake the pan for 1 1/2 minutes, or until the mustard seeds pop. Swirl the spiced oil into the lentils. Adjust the amount of salt and lemon juice, if needed, serve at once.