Smoked Salmon with Horesradish Sauce

1/2 cup low-fat sour cream
Smoked salmon, 2-4 ounces per person
2 tablespoons Horseradish sauce or more to taste
1 medium sweet onion, finely chopped
Horseradish Sauce
1 cup fresh horseradish root, peeled and cut into 1/2-inch cubes
1/4 cup white vinegar, or more if necessary
1/2 teaspoon salt
Put the horseradish root cubes in a food processor and grind them to fine particles. This will take 3-4 minutes. Be careful not to inhale the very irritating fumes.
Pour the white vinegar onto the ground horseradish until it is thoroughly moist.
Season with salt and mix well.
Store the prepared horseradish in the refrigerator in a tightly covered container and use it as a condiment.

Mix the sour cream with the prepared horseradish.
Serve individual portions of smoked fish, accompanied by the chopped onion and additional Horseradish Sauce.