Carl's Jr. knows how to sell hamburgers.

The fast-food restaurant chain can now ad recent Sports Illustrated Swimsuit Issue cover girl Kate Upton to its growing list of sexy women it's gotten to roll around seductively with one of their signature sandwiches.

"A spicy twist on a classic burger, the new Southwest Patty Melt features a charbroiled beef patty, with sliced jalapeños, grilled onions, pepper-Jack cheese and spicy Santa Fe sauce, all on grilled sourdough bread," reads the description of the company's latest burger - but it's Kate who adds all the heat.

It's been a busy month for 19-year-old Upton, in addition to Sports Illustrated she recently starred in a sexy photoshoot for Esquire. She revealed in the magazine that she's proud of her bikini body.

And now she joins the likes of Paris Hilton, Kim Kardashian, Audrina Patridge and Padma Lakshmi as a spokesperson for Carl's Jr. Check out her smokin' video below!