Preheat oven to 325 degrees. Toast bread slices in oven on a baking sheet, turning once, until golden, about 10 minutes.
Spread 2 teaspoons cream cheese on each toast. Divide cucumber, salmon, onions, and capers among toasts; season with pepper. Squeeze lemon juice on top.
I made these for a party and they were a big hit! I'll know to make more next time. You can also buy rye crips that have already been baked.