"I think from the minute [Colin and I] met, I just felt safe, which is always a great place to be with another actor," Kidman, 50, said.
The 41-year-old actor agreed, stressing that at the end of the day, it's all just a part of the job.
"You get through [those scenes] as quickly as you can, while not rushing it at the same time. It's very much business," Farrell said. "You're there to tell a story. You're there to honor the characters that have been written by somebody else and whose voice you are now beginning to adapt to yourself. You hear, 'Cut,' and everyone looks away, and you make sure that the person you're working with has cover."
Kidman, who plays Farrell's wife in the film, added that those particular scenes are often essential to telling a good story.
"As soon as I take myself out of the equation, it's just the storytelling," she said. "These particular scenes are very much needed for the relationship. They say so much."
Despite the film's seemingly disturbing nature, Kidman's husband, Keith Urban, is definitely a fan.
"Keith saw it in Cannes, and he flipped out," she admitted. "He was completely entranced."
The Oscar-winning actress is also continuing to speak out about domestic violence, stating that it's an "important" conversation to have.
"I've worked for decades for UN Women and violence against women, and it's never been heard so loudly as it is now," Kidman, who won an Emmy for her role as a victim of domestic violence in Big Little Lies, said. "Because for two decades, we've been desperately trying to having UN Women and eradicating violence against women. We've spent so long working for this cause."
Kidman added that she still speaks often with her Big Little Lies co-star Reese Witherspoon.
"I text and speak to her regularly," she said. "Pretty much daily right now."
Watch below for Witherspoon's emotional statement on sexual assault.