Preheat oven to 375 degrees F. Place a thin layer of oil on a baking dish.
Slice in half lengthwise, remove the seeds, wash and set aside.
In a large sauté pan heat oil over medium heat. Add onions and cook until soft for about 5 minutes.
Stir in the garlic, chili powder, cumin and paprika, season with salt & pepper, and cook for another 1-2 minutes.
Add the black beans, spinach, quinoa, and tomatoes, and mix together to fully combine. Cook over medium heat until the mixture is heated through, about 5 minutes. Stir in fresh cilantro.
Use a spoon to fill peppers with quinoa stuffing.
Arrange peppers in a large baking dish and cover with tinfoil. Bake for 25 minutes.
Remove peppers from the oven. Garnish with chopped cilantro and serve immediately.