  We present observations of an extreme radio flare, VT J024345.70-284040.08,
hereafter VT J0243, from the nucleus of a galaxy with evidence for historic
Seyfert activity at redshift $z=0.074$. Between NRAO VLA Sky Survey
observations in 1993 to VLA Sky Survey observations in 2018, VT J0243 rose from
a ${\sim}$GHz radio luminosity of $\nu L_\nu \lesssim 10^{38}$ erg s$^{-1}$ to
$\nu L_\nu{\sim}10^{40}$ erg s$^{-1}$, and still continues to brighten. The
radio spectral energy distribution (SED) evolution is consistent with a nascent
jet that has slowed over ${\sim}3000$ days with an average $0.1 < \langle \beta
\rangle < 0.6$. The jet is energetic (${\sim}10^{51-52}$ erg), and had a radius
${\sim}0.7$ pc in Dec. 2021. X-ray observations suggest a persistent or
evolving corona, possibly associated with an accretion disk, and IR and optical
observations constrain any high-energy counterpart to be sub-Eddington. VT
J0243 may be an example of a young, off-axis radio jet from a slowly evolving
tidal disruption event. Other more mysterious triggers for the accretion
enhancement and jet launching are possible. In either case, VT J0243 is a
unique example of a nascent jet, highlighting the unknown connection between
supermassive black holes, the properties of their accretion flows, and jet
launching.
