In a small bowl, combine mayonnaise, green onion, dill weed, capers, horseradish, and pepper; set aside.
Spread butter thinly over pumpernickel bread slices; spread mayonnaise mixture on each bread slice. Divide salmon and cucumber slices evenly over 4 slices of bread; top with remaining bread slices.
Cut each sandwich in half diagonally. May also cut in quarters or small rounds (your choice)
Transfer to individual serving plate and serve.
Yields 4 whole sandwiches or 8 halves or 16 fourths.
Making Tea Sandwiches Ahead of Time:
If you need to make tea sandwiches in advance and need to keep them from drying out, cover them loosely with a sheet of wax paper and then place a damp kitchen towel over the wax paper (never place a damp towel directly on top of the bread because the sandwiches will become soggy). Refrigerate.
When ready to serve, remove from refrigerator. Uncover the sandwiches just before serving.
Smoked Salmon Sandwiches on Pumpernickel Recipe: https://whatscookingamerica.net/sandwich/smsalmonsand.htm