  We present the analysis of TESS optical photometry of WASP-121b, which reveal
the phase curve of this transiting ultra-hot Jupiter. Its hotspot is located at
the substellar point, showing inefficient heat transport from the dayside (2870
K) to the nightside ($<$ 2200 K) at the altitudes probed by TESS. The TESS
eclipse depth, measured at the shortest wavelength to date for WASP-121b,
confirms the strong deviation from blackbody planetary emission. Our
atmospheric retrieval on the complete emission spectrum supports the presence
of a temperature inversion, which can be explained by the presence of VO and
possibly TiO and FeH. The strong planetary emission at short wavelengths could
arise from an H$^{-}$ continuum.
