Stephen Colbert and Jake Gyllenhaal bonded over sourdough starter

Jake Gyllenhaal was the first guest on Tuesday night's episode of "The Late Show with Stephen Colbert" to talk about the "Sondheim 90th Birthday" performance.

But he started off shushing Colbert.

"I have sourdough rising," Gyllenhaal whispered. "It's resting. My sourdough's resting."

Colbert whispered back "Is that something that sourdough has to do? It has to rest?"

The late-night host than asked the "Spider-man" actor if he's become a part of the "sourdough cult" which apparently has become a thing as people are at home due to the pandemic.

"As my hair has grown longer and as I've sort of slowly inched into the hipster world, I've found myself falling in love with sourdough," Gyllenhaal said.

With nothing to do, the star explained, a friend who owns the Mill Bakery in San Francisco graciously agreed to teach him about dough starters.

Turns out Colbert is right there with him, and pulled out his own sourdough starter.

"It certainly smells sour," said Colbert who added that his niece is making sourdough bread. "It smells like yogurt."

While a newbie himself, Gyllenhaal offered Colbert some tips on how to move forward with the starter.

"I have no idea what motivates anyone to watch television anymore, so it is possible this conversation right now is either getting Super Bowl ratings or people are scrambling for the remote right now to click over to anything else," Colbert joked.