Prepare your flax egg. Combine 1 tbsp of ground flax seeds with 2 tbsp of water in a small bowl and set aside.
Drain and rinse the black beans. Place them on a clean towel and pat dry.
Add the black beans, flax egg, breadcrumbs, and onion to a food processor and blitz until all ingredients are evenly combined. Avoid over-blending as this can result in mushier burgers. Place in a large bowl.
Combine the remaining ingredients in a small bowl and add to the black bean mixture. Doing this separately can help ensure the spice powders are mixed evenly into the burgers, without over blending.
Divide the mixture into 3-4 parts, roll them up into balls and flatten them so that they form burger patties.
Fry the patties on a hot pan with oil, for 2-3 minutes on each side.
Serve any way you like to enjoy a burger.