Place half of the salmon in a food processor. Turn on and blend until minced, almost the texture of ground beef. You don’t want it over-processed. Transfer to a bowl. Do the second batch of the salmon. (I do this in batches to prevent over blending the salmon).
In a large bowl, combine the salmon, garlic, chives, onion powder, cayenne, paprika, lemon zest salt, pepper, egg and 2 teaspoons cassava flour. Stir to combine.
Line a baking sheet with parchment paper. Form salmon into 4 equal-sized patties and place on baking sheet. Transfer burgers to the fridge so that it firms up a bit and is easy to work with, 10 to 15 minutes.
While the salmon is in the fridge, in a bowl add the sour cream, chives, salt, pepper, white vinegar and onion powder. Stir to combine.
Heat a nonstick skillet over medium heat with avocado oil. Sprinkle 1/2 teaspoon of cassava flour on each burger. Using your hands, reshape the salmon burgers into patties, pressing the cassava flour into the patties.
Transfer the patties to the hot skillet and cook until a golden-brown crust has formed on each side, about 3 minutes per side.
Top each burger with a dollop of sour cream sauce and enjoy!