  We report on the high-resolution spectroscopic observations of two planetary
transits of the hot Jupiter KELT-7b ($M_{\rm p}$ $=$ 1.28 $\pm$ 0.17 M$_{\rm
Jup}$, $T_{\rm eq}$ $=$ 2028 K) observed with the High Optical Resolution
Spectrograph (HORuS) mounted on the 10.4-m Gran Telescopio Canarias (GTC). A
new set of stellar parameters are obtained for the rapidly rotating parent star
from the analysis of the spectra. Using the newly derived stellar mass and
radius, and the planetary transit data of the Transiting Exoplanet Survey
Satellite (TESS) together with the HORuS velocities and the photometric and
spectroscopic data available in the literature, we update and improve the
ephemeris of KELT-7b. Our results indicate that KELT-7 has an angle $\lambda$ =
$-$10.55 $\pm$ 0.27 deg between the sky projections of the star's spin axis and
the planet's orbital axis. By combining this angle and our newly derived
stellar rotation period of 1.38 $\pm$ 0.05 d, we obtained a 3D obliquity $\psi$
= 12.4 $\pm$ 11.7 deg (or 167.6 deg), thus reinforcing that KELT-7 is a
well-aligned planetary system. We search for the presence of H$\alpha$, Li I,
Na I, Mg I, and Ca II features in the transmission spectrum of KELT-7b but we
are only able to determine upper limits of 0.08-1.4 % on their presence after
accounting for the contribution of the stellar variability to the extracted
planetary spectrum. We also discuss the impact of stellar variability in the
planetary data. Our results reinforce the importance of monitoring the parent
star when performing high-resolution transmission spectroscopy of the planetary
atmosphere in the presence of stellar activity.
