Using a mandolin or sharp knife, slice cucumber into ⅛-inch thick slices.
Add the sliced cucumber, cream cheese, smoked salmon, sliced onion, capers, dill, everything bagel seasoning, salt, and pepper to a large deli container or glass jar. Cover and shake till all the ingredients are combined.
Eat immediately, either directly from the jar or serve in a bowl and top with additional fresh dill to garnish.