Heat 1 tablespoon of olive oil in a large pot over medium-high heat. Add 3 diced carrots and cook for 3 minutes.
Blend 2 Roma tomatoes, ½ onion, 2 garlic cloves, ¾ teaspoon of kosher salt, ¼ teaspoon of black pepper, and ¼ teaspoon of dried Mexican oregano until smooth.
Add the tomato mixture to the pot with 5 cups of vegetable broth, 1 cup of rinsed dry brown lentils, 1 large diced russet potato, and 12 cilantro sprigs.
Bring to a boil, then cover and simmer over low heat for 28-30 minutes, until the lentils and potato are tender. Remove the cilantro sprigs and serve.
