Aromatic dill and smoked salmon are a classic pairing, while a simple-yet-flavorful lemon-caper butter add zing to these tea sandwiches.
In the bowl of a food processor fitted with the metal blade, combine butter, lemon juice, zest, capers, and salt. Pulse until combined and most of the capers are broken up, about 15 seconds.
Spread a thin layer of caper butter on two slices of bread. Cover one slice with a layer each of salmon and dill sprigs, and top with other bread slice. Use a serrated knife to trim crusts and cut in half diagonally into two triangles. Repeat with remaining ingredients. Cover with damp papers towel until ready to serve.