Who anointed Charlemagne holy roman emperor?

It happened in Rome, on Christmas night of the year 800, when pope Leo 3rd , at the end of the mass in the basilic of Saint Peter, crowned Charles of the Franks as ''Ceasar and Emperor of the Romans''. Charles was dressed as a roman senator, the frank army officers in the church claimed him saying ''To Charles the Great, pious emperor krowned by God, life and victory'', while the roman people in the square in front of the basilical church claimed him as ''Charles Augustus, Great and pious Emperor of the Romans''.

To note: Charlemagne was entitled Ceasar and Emperor of the Romans, not Holy Roman Emperor. The first who took this tile was only Otto 1st of Saxony in 963 a.D.