Start by thinly slicing the cucumber. For best results, use a mandoline or a sharp knife to ensure even slices. Place the cucumber slices on a paper towel to absorb any excess moisture.

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

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

Using a sharp knife, carefully cut off the crusts of the sandwiches. Then, cut each sandwich into small rectangles or triangles for a classic tea sandwich presentation. Serve immediately or chill in the refrigerator until ready to serve.