Preheat your oven to 375°F (190°C).
Rinse the lentils under cold water and drain. In a medium saucepan, bring the vegetable broth to a boil, add the lentils, reduce heat to low, cover, and simmer for about 20 minutes or until lentils are tender.
While the lentils are cooking, prepare the peppers by slicing off the tops and removing the seeds and membranes. Chop the tops and set aside to use in the filling.
Heat the olive oil in a large skillet over medium heat. Sauté the chopped onion and bell pepper tops until softened, about 5 minutes. Add the garlic and cook for an additional minute until fragrant.
Stir in the diced tomatoes, cumin, paprika, cinnamon, and cayenne pepper. Cook for 5 minutes, allowing the flavors to meld.
Once the lentils are cooked, drain any excess liquid, and add them to the skillet. Stir the mixture well and season with salt and black pepper.
Fill each bell pepper with the lentil mixture, packing it lightly to fit as much as possible.
Place the stuffed peppers upright in a baking dish and cover loosely with foil.
Bake in the preheated oven for 30-35 minutes, or until the peppers are tender and the filling is heated through.
Remove from the oven, garnish with fresh parsley, and serve hot.