Our Sun is powered by the fusion of hydrogen into helium that proceeds in the solar core via two distinct mechanisms: dominant proton-proton (pp) chain and sub-dominant Carbon-Nitrogen-Oxygen (CNO) cycle. Solar neutrinos are emitted in electron-flavour eigenstate along several distinct reactions of both cycles, each characterized by a specific energy spectrum and flux. These so-called solar neutrinos are the only direct probe of the energy production mechanism in the Sun and stars in general. Borexino, a 280-ton liquid scintillator detector that was taking data from May 2007 to October 2021 at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy, is the only experiment to perform a comprehensive spectroscopy of pp chain solar neutrinos and to prove the existence of CNO cycle. This was made possible thanks to an unprecedented radio-purity and thermal stability of the detector. This contribution is focused on the Borexino measurement of CNO solar neutrinos, that allowed us to exclude the absence of CNO signal with high statistical significance. In addition, we used the CNO flux measurement together with the 8B flux stemming from the global analysis of all solar neutrino data to evaluate the abundance of C and N with respect to H in the Sun with solar neutrinos for the first time. Our result agrees with the high metallicity spectroscopic photospheric measurements and shows a about a 2 sigma tension with the low metallicity ones.