Stir in 15 ounces of diced tomatoes, 1 cup of dried lentils, and 15 ounces of drained black beans. Then, sprinkle in 1 teaspoon of chili powder, 1/2 teaspoon of cumin, 1/2 teaspoon of black pepper, and 1/2 teaspoon of kosher salt. Mix in 4 cups of vegetable broth.
Turn up the heat and bring the mixture to a gentle boil. Once bubbling, reduce the heat to a simmer, then cover the pot. Let it simmer for about 25-30 minutes.
During the last few minutes of cooking, occasionally stir the soup to prevent sticking and check for the doneness of the lentils and carrots.
Taste the soup and adjust seasoning as necessary. Ladle the soup into bowls and serve hot.