  We present early spectral observations of the very slow Galactic nova
Gaia22alz, over its gradual rise to peak brightness that lasted 180 days.
During the first 50 days, when the nova was only 3--4 magnitudes above its
normal brightness, the spectra showed narrow (FWHM $\approx$ 400 km s$^{-1}$)
emission lines of H Balmer, He I, He II, and C IV, but no P Cygni absorption. A
few weeks later, the high-excitation He II and C IV lines disappeared, and P
Cygni profiles of Balmer, He I, and eventually Fe II lines emerged, yielding a
spectrum typical of classical novae before peak. We propose that the early
spectra of Gaia22alz are produced in the white dwarf's envelope or accretion
disk, reprocessing X-ray and ultraviolet emission from the white dwarf after a
dramatic increase in the rate of thermonuclear reactions, during a phase known
as the ``early X-ray/UV flash''. If true, this would be one of the rare times
that the optical signature of the early X-ray/UV flash has been detected. While
this phase might last only a few hours in other novae and thus be easily
missed, it was possible to detect in Gaia22alz due to its very slow and gradual
rise and thanks to the efficiency of new all-sky surveys in detecting
transients on their rise. We also consider alternative scenarios that could
explain the early spectral features of Gaia22alz and its unusually slow rise.

High Energy Astrophysical Phenomena;Solar and Stellar Astrophysics