The reality star was spotted out with the rapper on Monday night – the same day PEOPLE confirmed her split from Houston Rockets player James Harden.
The Kocktails with Khloé host sported a white jumpsuit with a champagne-colored overcoat. Montana opted for a more casual look, wearing black jeans and a red jacket.
"They came together and left together. They also sat next to each other at the same table. They were super cozy but not touchy-feely," an onlooker at The Nice Guy tells PEOPLE. "They made each other laugh, and they were genuinely having a great time together over light bites and drinks at the restaurant. They were showing each other things on their phone, but in a friendly way. No intimacy or engagement in that way, but you can tell that there is still a spark there."
As it turns out, the exes were both celebrating the birthday of a mutual friend: actor Dorion Renaud, who even posted an Instagram of himself sandwiched between Kardashian and Montana.
"Oh my @DorionRenaud look what hanging out for your birthday did lol rumors rumors rumors! stop making nothing into something kids," she tweeted Tuesday.
The two previously had an on-and-off relationship, and the rapper has since been linked to Sanaa Lathan and reality star Dorothy Wang.
Oh my @DorionRenaud look what hanging out for your birthday did lol rumors rumors rumors! stop making nothing into something kids— Khloé (@khloekardashian) February 9, 2016
Kardashian and Harden began dating over the summer, but a source previously told PEOPLE that Kardashian's estranged husband Lamar Odom's health crisis – which prompted her to call off their divorce for the time being – took a toll on the couple's relationship.
The Keeping up with the Kardashians star told PEOPLE that Harden was "supportive and awesome" as she stood by Odom's side.
"It hasn't been easy. James obviously has wanted to see her more and be with her more, but she's felt like she needed to stay in L.A. to be with her family and to deal with Lamar stuff," a source close to the family said. "That has put some strain on things."
Kardashian told PEOPLE then that she would understand if things got "too overwhelming" for Harden amid Odom's recovery.
But it looks like Kardashian is ready to dive back into dating: She uploaded her OKCupid profile on her app and website Monday.
Reporting by MELODY CHIU