In a small mixing bowl, combine salmon cream cheese, capers, chives and lemon juice. Stir to combine thoroughly.
Make a pastry bag by cutting a small triangle out of the bottom corner of a large zip-top bag. Place a medium sized star pastry tip on the inside of bag and fit tightly into hole. Hold pastry bag upright with 1 hand and scoop salmon cream cheese mixture into the bag with other hand. Secure top and refrigerate until ready to use.
In a small bowl, blend the butter and tarragon and set aside.
To make sandwiches, spread tarragon butter on 2 slices of bread and place 6 to 8 cucumber slices between them. Repeat to make 15 sandwiches. Use a 3-inch flower shaped cookie cutter to stamp out sandwich flowers.
Arrange sandwiches on serving platter. Remove pastry bag from refrigerator and pipe salmon cream cheese mixture on top of each sandwich flower.