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

Using a sharp knife or mandoline, thinly slice the cucumber. For extra crispiness, lightly salt the cucumber slices and let them sit for 10 minutes, then pat them dry with a paper towel to remove excess moisture.

Spread a thin layer of butter on one side of each bread slice (if using). Then, spread a generous layer of the 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.

Using a sharp knife, carefully trim off the crusts for a clean, elegant look. Cut each sandwich into quarters or smaller triangles for dainty tea sandwiches. Arrange them on a platter and serve immediately, or cover with a damp cloth to keep them fresh until serving.