Hydroxycinnamoyl transferase that catalyzes the transfer of an acyl from benzoyl-CoA to tryptamine, to produce benzoyl tryptamine. Serotonin and tyramine serve as acyl acceptors in vitro. Can use p-coumaroyl-CoA, and to a lesser extent caffeoyl-CoA, as acyl donors. Belongs to the plant acyltransferase family.