Ron Baron, founder of Baron Capital, is a Tesla shareholder and a big believer in Elon Musk's vision of the future. Baron believes Tesla can grow sales to $1 trillion in 12 years.

Buy-and-hold investor Ron Baron told CNBC on Tuesday his biggest mistake was not investing in Jeff Bezos' Amazon.

"I didn't invest in him. How could I miss it?" said Baron, the billionaire founder of Baron Capital, which has $28.3 billion in assets under management.

In an interview on "Squawk Box," Baron said that back in 1999, his firm was suffering from a huge investment loss in Sotheby's, which was implicated in a price-fixing scandal. At the time, Baron said he was trying to persuade Bezos to invest in Sotheby's.

"Here I am trying to get him to buy this company that I have an investment in and I'm trapped instead of focusing on, 'Oh my God, this guy has changed the world,'" Baron said. "My biggest mistake was not investing in Amazon."