The pair headed to the Boston Manor branch of Harvester in London last night (27 October) after Simon made a promise to Stevi on live TV that he would join him for a bite to eat at the cheap and cheerful restaurant.
Fellow diners couldn't believe their eyes when they saw the music mogul rock up with his contestant. And they were even more amazed when he chose a £4.99 chips and scampi meal from the menu!
Despite being used to slap-up grub from exclusive haunts such as The Ivy, Simon seemed pretty chuffed with his dinner - and the unlimited salad bar.
"Thanks for dinner Stevi," he tweeted. "Scampi and chips at the Harvester. Delicious."
Replying to a Twitter user who had enquired about how he found the salad bar, Simon simply added: "All you can eat. Boom!"
Stevi, meanwhile, seemed a little apprehensive before his very important dinner date. He told his followers: "Ok, so I'm having a meal at Harvester with the boss man himself Mr Simon Cowell and I'm sooooo nervous xx."
However, it seems he need not have worried as the pair had a great time. In fact, by the end of the night Stevi was even referring to Simon as his "best friend"!
"Really enjoyed my lovely dinner with my best friend and mentor @SimonCowell it was amazing such a great night thank you bossman xx," he added. Aww!
During their dinner, fellow restaurant-goers jumped on Twitter to share their celebrity spot. One fan, who managed to snap a picture of the pair tucking into their dinner, told her followers: "So @SimonCowell is at my local Harvester with @THESTEVIRITCHIE. Casual Monday evening #amazing #xfactor."
And the staff couldn't believe their eyes too. Before heading home, Simon and Stevi joined the team - including the chefs - for a group photo.