  Early observations of Type Ia supernovae (SNe$\,$Ia) provide essential clues
for understanding the progenitor system that gave rise to the terminal
thermonuclear explosion. We present exquisite observations of SN$\,$2019yvq,
the second observed SN$\,$Ia, after iPTF$\,$14atg, to display an early flash of
emission in the ultraviolet (UV) and optical. Our analysis finds that
SN$\,$2019yvq was unusual, even when ignoring the initial flash, in that it was
moderately underluminous for an SN$\,$Ia ($M_g \approx -18.5\,$mag at peak) yet
featured very high absorption velocities ($v \approx
15,000\,\mathrm{km\,s}^{-1}$ for Si II $\lambda$6355 at peak). We find that
many of the observational features of SN$\,$2019yvq, aside from the flash, can
be explained if the explosive yield of radioactive $^{56}\mathrm{Ni}$ is
relatively low (we measure $M_{^{56}\mathrm{Ni}} = 0.31 \pm 0.05\,M_\odot$) and
it and other iron-group elements are concentrated in the innermost layers of
the ejecta. To explain both the UV/optical flash and peak properties of
SN$\,$2019yvq we consider four different models: interaction between the SN
ejecta and a nondegenerate companion, extended clumps of $^{56}\mathrm{Ni}$ in
the outer ejecta, a double-detonation explosion, and the violent merger of two
white dwarfs. Each of these models has shortcomings when compared to the
observations; it is clear additional tuning is required to better match
SN$\,$2019yvq. In closing, we predict that the nebular spectra of SN$\,$2019yvq
will feature either H or He emission, if the ejecta collided with a companion,
strong [Ca II] emission, if it was a double detonation, or narrow [O I]
emission, if it was due to a violent merger.
