In blender container, place broth, 1/2 can diced tomatoes, pumpkin, cocoa powder, cider vinegar, chipotle chili, oregano, cumin, and cinnamon and blend until smooth. Add tomato mixture and drained lentils to saucepan with browned grounds mixture; bring to a boil, reduce heat to medium-low, and simmer until lentils are tender, stirring occasionally, about 40 minutes.