'Flipping Out' Star Jeff Lewis Shades Jenni Pulos with Red 'X' in Promo Photo

Jeff Lewis fired a major shot at his longtime "Flipping Out" co-star, Jenni Pulos ... and it's sure to make fans flip out.

The famed house flipper just shared a promotional image for the upcoming Tuesday night premiere of season 11 of the show on social media ... with one major edit -- a huge red "X" over Pulos' face.

Lewis is standing between Jenni and his partner, Gage Edward. The caption's pretty innocuous, but Jeff's clearly letting it be known ... his relationship with Pulos is dunzo.

Jeff and Jenni reportedly had a falling out after an explosive fight -- which will be aired on the upcoming season -- and haven't spoken since. As for what led to the fight ... she reported Jeff to the network, claiming he was abusive, harassed her and generally created a hostile working environment.

Lewis followed up with his own claim ... that he and Pulos had been faking their business relationship for the cameras and she hadn't actually worked for him for years.

Regardless, the 2 had been together on screen since the hit reality series debuted in 2007 ... and both are executive producers.