Bill Gates offered a sweet and funny video tribute to his billionaire pal Warren Buffett Sunday in honor of his 90th birthday.

Doing his best Martha Stewart impression, and with Randy Newman's "You Got a Friend" playing in the background, Gates made a delicious-looking Oreo cake, complete with Buffett's face on the top, drawn in chocolate icing.

In the end of the 60-second video, Gates cuts a slice, puts it on a plate with a fork, and leaves the message "Happy 90th birthday Warren" in Oreo dust.

Happy 90th birthday, Warren! pic.twitter.com/8nH2EulTR4

— Bill Gates (@BillGates) August 30, 2020

Buffett is a notorious dessert-a-holic, known for chugging a half-dozen cans of Coke every day (Buffett is a big Coca-Cola (KO) investor).

His company, Berkshire Hathaway (BRKA), also owns See's Candies.

The cake was a special tribute to Gates' friendship with Buffett. In 2016, Gates recounted a story on his blog about how he caught Buffett eating his favorite dessert for breakfast: Oreos.

"One thing that was surprising to learn about Warren is that he has basically stuck to eating what he liked when he was six years old," Gates wrote.

"I remember one of the first times he stayed at our house and he opened up a package of Oreos to eat for breakfast.

Our kids immediately demanded they have some too. He may set a poor example for young people, but it's a diet that somehow works for him."

Gates and Buffett met on July 5, 1991, when Gates' mother invited the then-Microsoft-CEO to the Gates family vaction home in Hood Canal, Washington, to meet Buffett, whom she also invited.

Gates, in a blog post, said he was reluctant at first, but Buffett peppered him with smart questions about Microsoft's future that Gates said he never before encountered (how Microsoft (MSFT) could expect to compete with IBM and what skillsets and pricing Microsoft expected to excel at).

"It was a deep friendship from our very first conversation," Gates wrote.

Together, Gates and Buffett started The Giving Pledge, a philathropic movement of the world's wealthiest people to give away the majority of their wealth to charity.

The pledge now has 200 signatories, including Mark Zuckerberg, MacKenzie Bezos, Michael Bloomberg, Carl Icahn, Elon Musk, Stephen Schwarzman and CNN founder Ted Turner.

The Gates Foundation, Bill and Melinda Gates' charity, became one of Berkshire Hathaway's largest shareholders in 2018.

Gates left Berkshire's board (along with Microsoft's) in 2020, to focus on his philanthropy.