Soften the cream cheese: Leave it at room temperature for 20–30 minutes so it mixes smoothly and spreads easily.
Mix the lemon-dill spread: In a bowl, combine cream cheese, lemon juice, lemon zest, dill, capers (if using), Dijon (if using), salt, and pepper. Stir until smooth.
Adjust lemon and salt to taste; you want bright, savory, and balanced.
Prep the bread: If your bread is very soft, lay slices out for 5 minutes to dry slightly. If you like, lightly butter one side of each slice to prevent sogginess.
Assemble the sandwiches: Spread a generous layer of the lemon-dill cream cheese on each slice. Add a single, even layer of smoked salmon over half the slices.
Add a few thin cucumber slices if using.
Close and press: Top with the remaining bread, cream cheese side down. Press gently so everything adheres without squishing.
Trim and slice: Using a sharp serrated knife, trim crusts for a clean edge. Slice each sandwich into three or four fingers or into neat triangles.
Garnish and serve: Arrange on a platter.
Sprinkle with a tiny pinch of dill or lemon zest, if desired. Serve right away or cover lightly and chill for up to 1 hour.