This is an authentic Mexican recipe from Cueva Grande, Valparaiso, Zacatecas, Mexico. The only thing I changed was the addition of the potatoes.
Bring the water to a boil in a soup pot with 3 cloves of garlic. Stir in the lentils and 1 1/2 tablespoons of chicken bouillon. Simmer over medium-low heat until lentils are almost soft, about 1 hour.
Heat extra-virgin olive oil in a skillet, and cook and stir the onion and 2 chopped cloves of garlic until the onion becomes translucent, about 5 minutes. Add the tomato and continue to cook and stir until the tomato releases its juice, about 5 more minutes. Stir the tomato mixture into the lentil soup along with cumin and 2 more teaspoons of chicken bouillon, or to taste. Bring the soup to a simmer, stir in the nopales and potatoes, and cook over low heat until the potatoes are tender, about 20 minutes.
Per Serving: 187 calories; protein 11.9g; carbohydrates 33.7g; fat 1.2g; cholesterol 0.2mg; sodium 261.4mg.