In the image, which was taken in the desert, Longoriacan be seen wearing a huge sparkler on her left hand as she passionately kisses the TV president, who she has been dating since 2013.
The proposal comes as a surprise, since Longoria had ruled out walking down the aisle for a third time, saying last year: "Marriage and kids are not on the horizon."
She split from French basketball player Tony Parker to whom she was married for four years in 2011 and before that when she eloped with actor Christopher Tyler in 2002, before the marriage broke up in 2004.
However, Longoria has admitted that Baston makes her happier than ever before.
She said: "I'm truly in love, mostly ... every moment we get to spend together is a blessing.
"People want a secret to looking good, but there isn't one. I'm in love, that has a lot to do with it. I take good care of myself, it's no secret, I eat a healthy diet and I exercise..."
