  We use, for the first time, ab initio coupled-cluster theory to compute the
spectral function of the uniform electron gas at a Wigner-Seitz radius of
$r_\mathrm{s}=4$. The coupled-cluster approximations we employ go significantly
beyond the diagrammatic content of state-of-the-art $GW$ theory. We compare our
calculations extensively to $GW$ and $GW$-plus-cumulant theory, illustrating
the strengths and weaknesses of these methods in capturing the quasiparticle
and satellite features of the electron gas. Our accurate calculations further
allow us to address the long-standing debate over the occupied bandwidth of
metallic sodium. Our findings indicate that the future application of
coupled-cluster theory to condensed phase material spectra is highly promising.
