Heat the olive oil in a skillet over medium heat. Add the garlic and sauté for 30 seconds or until fragrant.
Add the chopped walnuts and stir well. Cook for 3 minutes, stirring periodically, or until fragrant.
Add the lentils, tomatoes, chipotle pepper, adobo sauce, oregano, cumin, and salt. Stir well and bring to a simmer. Cook for 10 minutes, or until thickened and fragrant. Season to taste with salt if desired.
