Mix salmon, spinach, egg, sour cream, and lemon juice in a bowl.
Combine the dill and onion with the flax meal in a second bowl. Pour into the egg and fish mixture. Combine well with hands or spoon.
Heat cooking fat in a frying pan over medium heat. Form 8 mounds to look like burger patties in your hands. The batter will be runny, press it as best you can and place in the hot oil. Fry for 2 to 3 minutes, flip and continue on the second side for another 2 to 3 minutes. You want each side to be golden brown and crispy. These patties only hold together if they are cooked long enough. If it is difficult to flip, leave them to cook longer then try again after a minute passes.
Serve with Keto Flatbreads, cheese, mayonnaise, and any other burger fixings you like.
Macros are calculated for 1 patty only. If using Keto Flatbreads add: 7.5 g fat, 5 g carb, 0.5 g net carb, 5.25 g protein per two pieces.