Bring 2 cups of water to a boil. Meanwhile, rinse and drain the black lentils. Add a Rapunzel bouillon cube to the water and stir. Add the lentils to the water, return to a boil, cover pot, and reduce to a low simmer. Cook for 30-35 minutes on low heat. When the lentils are done, you will use about 3/4 cup of the lentils and reserve the rest for another use.