Elon Musk at the 29th Annual Baron Investment Conference in 2022.Baron CapitalThe Baron Partners Fund, managed by Ron Baron, has outperformed the market in December.Tesla is the largest holding and is up 34% this month.Baron is BI's Investor of the Month for December.Thanks to his considerable bets on Elon Musk, investing legend Ron Baron is BI's Investor of the Month for December.His Baron Partners Fund (BPTRX), which he co-manages with his son Michael Baron, was up 15% month-to-date as of December 24, while the broader market was flat.