Love can be measured in many ways. For Mark Cuban, it was all about a simple 100% USDA beef patty slider.

When Cuban married his wife, Tiffany Stewart, he'd been a billionaire for roughly three years. He had one question for her before they tied the knot, he told the "Club Shay Shay" podcast last week: Would she go to White Castle with him?

"We're going to White Castle, and if you really love me, you'll eat a White Castle burger," said Cuban, 66. "And she did."

The couple met in 1997, seven years after Cuban sold his software startup MicroSolutions to CompuServe for $6 million. He became a billionaire in 1999, selling his second company Broadcast.com to Yahoo for $5.7 billion in an all-stock deal.

But Cuban wasn't always rich: He grew up in Pittsburgh in a working-class family, where his dad made a maximum of $40,000 a year upholstering cars. His mom worked "odd jobs" to make ends meet, he said. He attended Indiana University, where White Castles were "everywhere," he added.

Sharing that piece of his early life with Stewart probably built trust between the couple, says Robert Wickham, a relationships expert and associate professor of psychological sciences at Northern Arizona University.

Asking your partner if they'll go to White Castle with you isn't a one-way ticket to true love — anyone could agree to eat a burger — but their relationship likely benefited from Stewart's reaction, Wickham says.

"[Cuban is] thinking, 'OK, this person is in it for me. She wants to know me more,'" Wickham tells CNBC Make It. "She's in it for the right reasons."

Twenty-two years and three children later, Cuban and Stewart are still married.

A 'virtuous cycle' of openness and authenticity

In the early stages of a romantic relationship, partners look for signs of authenticity to gauge each other's trustworthiness says Wickham. It's a precursor to a more satisfying, intimate relationship, his research shows.

"Openness in a relationship, right from the get-go, tends to facilitate the authentic development of intimacy, trust and all the good things that are a part of fulfilling relationships," Wickham says.

If you frame a question like Cuban's as a test, you might not get very far: "Testing" your partner isn't exactly the epitome of openness or vulnerability.

But if you share an unexpected or important part of your life with someone you care about, and they reciprocate, you might be on the right track. The more open and vulnerable you are with your partner, the more you can foster a positive cycle of trust and intimacy, says Wickham.

"It feeds into this virtuous cycle where there's nothing hidden, there's nothing covert about your motives or about what's going on, everything's on the table," he says.

The advice extends beyond romantic relationships: Building trust by being yourself can lead to more successful friendships and business relationships, says Wickham. If your manager trusts you, they might give you important tasks more freely, for example.

"Much of what goes on is built on trust and relationships," Wickham says. "Authenticity is generally a good thing."

Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank," which features Mark Cuban as a panelist.

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