Katharine, 35, wore a black and pink floral ruffled maxi dress, black strappy sandals and mirrored shades.
The American Idol alum pulled her brunette locks into a low pony and added a thin pearl necklace.
David, 69, rocked a light pink button down that he left open and wore white undershirt underneath. The musician sported light wash jeans, aviators and a shiny black belt.
The pair dined at the Italian restaurant Il Pastaio in Los Angeles. David flashed a wad of cash and counted $100 bills in the parking lot.
Katharine and David walked down the aisle at St. Yeghiche Armenian Church in London in front of friends and family on June 28.
What are your thoughts on David and Katharine's lunch date? Sound off in the comments below!