In a recent interview on CNBCShake Shack founder and CEO of Union Square Hospitality Group, Danny Meyer, revealed his secret to hiring the best service professionals.

What matters most is that the job candidate has what Meyer calls “the hospitality gene.” Are they capable–with the right training–of providing exceptional service? “Nobody ever got hired at Shake Shack because they could tell us how many great milk shakes they’ve made in their career. They get hired for who they are,” says Meyer.

Creating a culture of service is so critical to the success of the Shake Shack model, Meyer says it took five years to open a second store (today there are 136 Shake Shacks around the world). “You can only grow as fast as you can grow people,” he says. In other words, Meyer only expands a brand when he’s certain he can keep the culture in tact.

In his customer service book Setting the Table, Meyer writes, “Business, like life, is all about how you make people feel. It’s that simple, and it’s that hard.”

Meyer says training for emotional skills is next to impossible. The trick trick to hiring customer service champions who deliver superior hospitality is to hire genuine, happy, optimistic people. According to Meyer, the hospitality gene can be spotted in people who exude:

Optimistic warmth (genuine kindness), an insatiable curiosity to learn, a strong work ethic, and empathy toward people’s feelings.

The Apple Store ‘Hires for Smiles’

Meyer’s approach reminds me of another brand’s hiring model–Apple. When I was conducting my research for the first book on the Apple Retail store model, Apple managers told me they “hires for smiles.”

The ideal Apple Store employee knows a little about computers and a lot about people. One Apple hiring manager told me he would prefer to hire a teacher who doesn’t know computers over a computer expert who can’t teach.

Apple doesn’t hire for technical knowledge; it hires for personality. Anyone can learn to talk about an iPad, but if they don’t have the hospitality gene, it doesn’t matter.

A few years after my Apple book was published, I was having a conversation with George Blankenship, the head of retail at Tesla. In his previous job, Blankenship sat a few doors down from Steve Jobs and helped to build the first 100 Apple stores.

Blankenship echoed the Apple approach to hiring word-for-word (he just replaced “computer” with “car”): “Carmine, I don’t hire former car dealers. I’d rather hire a teacher who has never sold cars over a car salesman who knows cars, but can’t teach.”

Apple, Danny Meyer’s restaurants, and yes, Tesla, are customer service champions because they focus on hiring for personality. Just as Apple hires people who are passionate about its products (and sharing those products with others), Meyer hires people who take joy in customer service and who want to share their enthusiasm with their customers.

Meyer is so convinced that hiring for culture fit is critical, he started a private-equity fund earlier this year called Enlightened Hospitality Investments. It only invests in companies that show a strong culture and a commitment to its employees. For Meyer, employees come first and customers are second–a recipe where everyone wins.