  We present dayside thermal emission observations of the hottest exoplanet
KELT-9b using the new MAROON-X spectrograph. We detect atomic lines in emission
with a signal-to-noise ratio of 10 using cross-correlation with binary masks.
The detection of emission lines confirms the presence of a thermal inversion in
KELT-9b's atmosphere. We also use M-dwarf stellar masks to search for TiO,
which has recently been invoked to explain the unusual \textit{HST}/WFC3
spectrum of the planet. We find that the KELT-9b atmosphere is inconsistent
with the M-dwarf masks. Furthermore, we use an atmospheric retrieval approach
to place an upper limit on the TiO volume mixing ratio of 10$^{-8.5}$ (at 99\%
confidence). This upper limit is inconsistent with the models used to match the
WFC3 data, which require at least an order of magnitude more TiO, thus
suggesting the need for an alternate explanation of the space-based data. Our
retrieval results also strongly prefer an inverted temperature profile and
atomic/ion abundances largely consistent with the expectations for a solar
composition gas in thermochemcial equilibrium. The exception is the retrieved
abundance of Fe$^+$, which is about 1-2 orders of magnitude greater than
predictions. These results highlight the growing power of high-resolution
spectrographs on large ground-based telescopes to characterize exoplanet
atmospheres when used in combination with new retrieval techniques.
