Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper.

Sauté the finely chopped onion in a skillet over medium heat until translucent, about 5 minutes. Add minced garlic and cook until golden brown.

Mash the black beans in a large bowl until mostly smooth but still chunky.

Combine all ingredients, folding in the sautéed onions, garlic, breadcrumbs, cumin, smoked paprika, cilantro, and either egg or flax egg until well blended.

Shape the mixture into patties about ½ inch thick and place on the prepared baking sheet.

Bake in the preheated oven for 25-30 minutes until firm and slightly crispy on the edges.

Toast the whole wheat buns until golden brown either in the oven or in a skillet.

Serve with your favorite toppings like sliced avocado or salsa.