Bake the sweet potatoes: Preheat oven to 400°F. Line a large baking sheet with aluminum foil and spray with nonstick cooking spray. Place halved sweet potatoes cut side down and poke each half with a fork a few times.Bake for 30-35 minutes until sweet potatoes are tender and cooked through. Remove from oven and let cool for 5 minutes. While sweet potatoes are baking, make the quinoa.
Cook the quinoa: Place quinoa in a fine-mesh sieve and rinse under cold running water for about 1 minute. Drain and transfer to a medium pot. Add in 1 cup of water and bring to a boil over high heat.Reduce heat to low, cover and simmer for 10-15 minutes, until quinoa is tender and cooked through. Let stand for 5 minutes, covered. Remove the lid and fluff with a fork.
Make the seasoning: In a small bowl, add the ground flax seed, ground cumin, coarse kosher salt, onion powder, chili powder, garlic powder, dried oregano and ground black pepper. Mix together and set aside.
Mash it up: In a large bowl, add the black beans and cooked sweet potatoes. Mash until the consistency is only slightly chunky. Some beans will be completely mashed and others will not. This will help create a nice texture.
Mix it all together: Add the cooked quinoa and combined spices. Mix it all together until all the ingredients are evenly distributed. hands and form into 8 burger patties, about 1/3 cup of mixture each.
Make the patties: Using your hands, form the mixture into 8 burger patties, about a heaping 1/3 cup of mixture per patty.
Cook the burgers: Line a large baking sheet with parchment paper and spray with nonstick cooking spray or olive oil. Place burger patties baking sheet and bake in 400°F oven for 20 minutes. Carefully flip over the patties and bake for another 20 minutes. Remove from oven and serve.