  We calculate the single spin asymmetry for the $e p \to e \Delta(1232)$
process, for an electron beam polarized normal to the scattering plane. Such
single spin asymmetries vanish in the one-photon exchange approximation, and
are directly proportional to the absorptive part of a two-photon exchange
amplitude. As the intermediate state in such two-photon exchange process is on
its mass shell, the asymmetry allows one to access for the first time the
on-shell $\Delta \to \Delta$ as well as $N^\ast \to \Delta$ electromagnetic
transitions. We present the general formalism to describe the $e p \to e
\Delta$ beam normal spin asymmetry, and provide a numerical estimate of its
value using the nucleon, $\Delta(1232)$, $S_{11}(1535)$, and $D_{13}(1520)$
intermediate states. We compare our results with the first data from the
Qweak@JLab experiment and give predictions for the A4@MAMI experiment.
