This paper reports the successful fabrication and test results of a novel 2815 MHz superconducting deflecting cavity operating in a TE-mode trapped in a quasiwaveguide structure with extremely high shunt impedance. The waveguide structure of this cavity allows for the free propagation of all higher order modes (HOMs) out of the cavity via the beam ports, eliminating the need for HOM dampers inside the cavity when operated with high beam current. The absence of HOM dampers greatly simplifies the cavity fabrication and operation at cryogenic temperatures. This cavity with its high shunt impedance is ideal for the spatial rotation of short bunches in a small physical space, a requirement for the generation of sub-picosecond short pulse X-rays in electron storage rings or luminosity upgrades of colliders.