Prepare mayo by mixing lemon juice, zest, white truffle oil, shallot and salt & pepper into mayo. Set aside.
Assemble canapes by adding a layer of mayo, and then salmon and cucumber slices. Top with extra lemon zest if desired (I did for the photos).
Serve immediately.
Notes
I bought salmon that had dill on top of it already... thus the dill in the photos. You could sprinkle some fresh or dried dill onto the salmon, but I would say that's optional.