JWST/NIRSpec rest-frame optical spectrum of the PJ308-21 quasar (black). Broad Balmer line emission (Hα, Hβ, Hγ, Hδ), strong Fe II, and [O III] emission is clearly seen. Top panel: quasar continuum fit (magenta curve). We highlight the line-free regions used for the continuum fit (pale blue). The orange curve shows the residuals. Bottom panel: Fe II line model (magenta). The fitted wavelengths are highlighted in pale blue. We fit the Fe II emission using the five multiplets template of Kovačević et al. (2010) and Shapovalova et al. (2012) (colored lines in the insets). The iron-subtracted spectrum (orange) was then used to fit the Balmer and nebular lines.