In a bowl, mix the softened cream cheese, chopped dill, lemon juice, salt, and pepper until smooth and well combined.

Using a sharp knife or a mandoline, thinly slice the cucumber. Pat the slices dry with a paper towel to remove excess moisture if desired.

Spread a thin layer of butter on one side of each bread slice (if using). Spread a generous layer of the herbed cream cheese mixture on the unbuttered side of each slice. Arrange the cucumber slices evenly over the cream cheese on half of the bread slices. Top with the remaining bread slices, cream cheese side down.

Trim the crusts off the sandwiches for a more elegant look, if desired. Cut each sandwich into quarters or smaller rectangles to create tea-time finger sandwiches. Arrange them on a platter and serve immediately.