Heidi Klum and Martin Kirsten
09/28/2012 at 06:00 AM EDT
and her bodyguard/rumored boyfriend Martin Kirsten stepped out for a late lunch Tuesday at Joe's Stone Crab in Las Vegas.
"They were very affectionate throughout the meal," an onlooker tells PEOPLE.
The couple enjoyed oysters, stone crab, pan-roasted sweet corn and filet mignon.
Earlier this month, a friend of Klum's told PEOPLE
that the relationship between the model-turned-mogul and Kirsten is "complicated" but that Kirsten is Klum's "no. 1 confidante."
While their relationship is yet to be publicly confirmed, during a recent appearance on Katie
, Klum spoke fondly of Kirsten, explaining that he has "cared for our four children and helped us tremendously" since working for her over the past four years.
– Jennifer Garcia