  Recent discoveries have demonstrated that planetary systems routinely survive
the post-main sequence evolution of their host stars, leaving the resulting
white dwarf with a rich circumsteller environment. Among the most intriguing of
such hosts is the hot white dwarf GD 394, exhibiting a unique $1.150\pm0.003$ d
flux variation detected in Extreme Ultraviolet Explorer (EUVE) observations in
the mid 1990s. The variation has eluded a satisfactory explanation, but
hypotheses include channeled accretion producing a dark spot of metals,
occultation by a gas cloud from an evaporating planet, or heating from a flux
tube produced by an orbiting iron-cored planetesimal.
  We present observations obtained with the Transiting Exoplanet Survey
Satellite (TESS) of GD 394. The space-based optical photometry demonstrates a
$0.12\pm0.01$ % flux variation with a period of $1.146\pm 0.001$ d, consistent
with the EUVE period and the first re-detection of the flux variation outside
of the extreme ultraviolet. We describe the analysis of the TESS light curve
and measurement of the optical variation, and discuss the implications of our
results for the various physical explanations put forward for the variability
of GD 394.
