  Context. Red supergiant stars are one of the latest stages in the evolution
of massive stars. Their photospheric convection may play an important role in
the launching mechanism of their mass loss; however, its characteristics and
dynamics are still poorly constrained. Aims. By observing red supergiant stars
with near infrared interferometry at different epochs, we expect to reveal the
evolution of bright convective features on their stellar surface. Methods. We
observed the M2Iab-Ib red supergiant star CE Tau with the VLTI/PIONIER
instrument in the H band at two different epochs separated by one month.
Results. We derive the angular diameter of the star and basic stellar
parameters, and reconstruct two reliable images of its H-band photosphere. The
contrast of the convective pattern of the reconstructed images is $5 \pm 1 \%$
and $6 \pm 1 \%$ for our two epochs of observation. Conclusions. The stellar
photosphere shows few changes between the two epochs. The contrast of the
convective pattern is below the average contrast variations obtained on 30
randomly chosen snapshots of the best matching 3D radiative hydrodynamics
simulation: $23 \pm 1~\%$ for the original simulation images and $16 \pm 1~\%$
for the maps degraded to the reconstruction resolution. We offer two hypotheses
to explain this observation. CE Tau may be experiencing a quiet convective
activity episode or it could be a consequence of its warmer effective
temperature (hence its smaller radius) compared to the simulation.
