8 of the most surprising revelations from Martha Stewart's candid new Netflix documentary

Martha Stewart said her father slapped her when she got engaged because her fiancé was Jewish.

Stewart revealed what it was like growing up with six siblings in Nutley, New Jersey. She said her drive for perfectionism came from her father, Edward Kostyra.

"Dad made each of us learn how to garden. He could grow anything," Stewart says in the documentary. "I was the ideal daughter. I wanted to learn, he had a lot to teach, and I listened."

"It was very obvious to everybody that I was his favorite," she added. "He thought I was more like him than the other children."

But Stewart said her father was also a "dissatisfied, unhappy human being" who would sometimes begin the day with a glass of red wine alongside his coffee. Frank Kostyra, one of Stewart's brothers, said their father would whip his children with a yardstick or the end of a belt.

Stewart said her father also hit her when she told him that she was engaged to Andrew Stewart.

"I went home and told my dad, and my dad slapped me," she recalled. "He slapped me hard on my face and said, 'No, you're not marrying him. He's a Jew.'"

"I remember getting that slap," Stewart added. "I was not at all surprised because he was a bigot and he was impulsive. But I said, 'I'm going to get married no matter what you think.'"

Stewart kissed a stranger while she was on her honeymoon in Italy.

Stewart and her husband took a five-month honeymoon around Europe after they got married when she was 19.

In the documentary, Stewart recalls a night when she visited a famous cathedral in Florence while Andrew opted to stay back in their hotel room.

"Listening to that amazing music in the cathedral, it was a very romantic place," Stewart said. "I met this very handsome guy. He didn't know I was married. I was this waif of a girl hanging out in the cathedral on Easter Eve."

"He was emotional, I was emotional, it was unlike anything I had ever experienced," she added. "And so, why not kiss a stranger?"

At this point, Cutler interjects and asks Stewart, "Were you being, what's the word I'm looking for…"

"Naughty?" Stewart asks.

"Was it naughty, or was it infidelity?" Cutler replies.

"It was neither naughty nor unfaithful," Stewart says. "It was just emotional, of the moment. That's how I looked at it. I wish we could all experience such an evening."

Stewart said she was the only woman at her firm when she was working as a stockbroker.

After working as a model in her teens and getting her history degree from Barnard College, Stewart set her sights on Wall Street. But in 1968, there were no other women at her firm.

"I had to sort of put my arm out like that," Stewart says in the documentary. "The stuff that went on in the back seat of the taxis, I'm not even gonna talk about."

But Stewart said she learned a lot during her stockbroker days, especially how to "behave around billionaires."

Stewart said she made a quarter of a million dollars a year at her firm. When she started to burn out, she quit Wall Street and moved her family to Turkey Hill Road in Westport, Connecticut.

Her first home renovation at Turkey Hill Road is why Stewart wanted to become a homemaker.

"If I hadn't had Turkey Hill, I would not be me right now," Stewart says in the documentary. "I would've been somebody; I would've been somebody else. I just wouldn't have been Martha Stewart, homemaker."

Stewart recalls how she renovated the entire estate, painting it from top to bottom and planting every single tree in the massive gardens with her own two hands.

"Those early days on Turkey Hill Road made me realize that I really did enjoy homemaking, homekeeping, keeping a home," she said.

Stewart said she loved entertaining at her home so much she decided to start a catering company. It became a million-dollar business.

"That was the beginning of Martha Stewart," she added.

Stewart and her husband both had affairs during their marriage.

Stewart discusses the fallout of her marriage to Andrew at length in "Martha," saying he repeatedly cheated on her while they were together. They were married from 1961 to 1990.

In the documentary, Stewart said one of her ex-husband's affairs was with a woman she had hired to do the flower arrangements at Turkey Hill. When the girl lost her apartment, Stewart invited her to move into the barn on their property.

"When I was traveling, Andy started up with her," Stewart said. "It was like I put out a snack for Andy."

"Young women, listen to my advice: If you're married, and you think you're happily married, and your husband starts to cheat on you, he's the piece of shit," she added. "And look at him as a piece of shit and get out of that marriage."

At this point in the documentary, Cutler interjects to ask Stewart if she'd had an affair early on in their marriage.

"I don't think Andy ever knew about that," Stewart says.

"He did say he knew about that," Cutler tells her. "He said he didn't stray from the marriage until you told him you had already strayed."

"Oh, that's not true, I don't think," Stewart replies.

"But what happened, you had an affair?" Cutler asks.

"I had a very brief affair with a very attractive Irishman," Stewart says. "I would've never broken up a marriage for it. It was nothing. It was like the kiss in the cathedral."

Stewart shared the heartbroken letters she wrote to her husband during their breakup.

"I cannot sleep, I cannot eat, my skin is worried and many lines that were not there are now there," she writes in one letter. "I'm agonizingly jealous of your other women. I can't bear that you use what we did together on others."

In another, Stewart wonders if her husband will marry his mistress "and keep her with my money so that she can paint herself portraits in the nude."

"It is very titillating, isn't it," she continues. "Maybe she will paint you in the nude also. I'd love to see that painting."

But the letters also reveal that Stewart pleaded with her husband not to walk away from their marriage.

"Give me another chance Andy, I am so sorry about so much," she writes. "Why does it have to be too late?"

While recounting her successful career in "Martha," Stewart said that she wasn't "really concentrating on my life."

"It sounds like you're expressing regret," Cutler says.

"Well, what is more important, a marriage or a career?" Stewart asks.

"You tell me," he says.

"I don't know," Stewart replies.

Stewart shared details about her 15-year relationship with Charles Simonyi, who developed Microsoft Word and Excel.

Stewart describes Simonyi as a "total genius" in the documentary, saying they "started to go everywhere together" at the beginning of their courtship.

Everything changed in 2004 when Stewart was found guilty of conspiracy, obstruction of justice, and making false statements to federal investigators amid the ImClone insider trading scandal. She served five months at the Federal Prison Camp Alderson in West Virginia, where she said Simonyi only visited her once.

"I don't think he liked hanging out with somebody in jail," Stewart says in the documentary. "He was out on his boat floating around the world. That was distressing to me."

Stewart said that when she was released in March 2005, Simonyi sent his private plane to pick her up. But he ended their relationship three years later while the couple was on a trip to Iceland.

"We were in bed, and he said, 'You know Martha, I'm going to get married. I'm going to get married to Lisa.'" Stewart recalled. "I said, 'Lisa who?' He hadn't told me a word."

"I thought that was the most horrible thing a person could do," she added. "How can a man who spent 15 years with me just do that?"

Stewart also revealed entries from the diary she kept while in prison.

Stewart kept a journal while she was in Alderson. On her very first day, she described being strip searched.

"Squat, arms out, cough. Embarrassing," she writes.

In the following entries, Stewart notes the "unhealthy bed set" in her prison cell, the "very poor quality of food" in the cafeteria, and the lack of fertilizer, pots, or seeds in the greenhouses.

She also revealed one instance in which she was forced to spend a day in solitary confinement without food or water after she brushed an officer's key chain while complimenting her outfit.

In perhaps the most revealing entry, Stewart discusses her sorrow while serving time.

"I feel very inconsequential today," she writes. "As if no one would miss me if I never came back to reality."