Check the salmon for bones and remove them with tweezers.
Place the salmon flank in a suitable dish.
Mix all the ingredients for the salt-spice mixture in a bowl and spread half of it in an even layer over the salmon.
Slice the beetroot into thin slices and layer them overlapping on the salmon.
Evenly distribute the rest of the salt mixture over the beetroot.
Place a board in the dish and put some weight on it.
Let the salmon brine for at least 1 day and a maximum of 2 days.
Remove the salmon from the dish and rinse it thoroughly with cold water.
Always store the salmon wrapped in plastic wrap or vacuum sealed in the refrigerator.
Slice the salmon into thin slices (slightly diagonally down to the skin) before serving and place them on a plate.
Mix the sour cream with horseradish and serve this with crackers, lemon wedges, and freshly ground black pepper.