It wasn't the cleanest of matches - Karatantcheva double faulted 14 times in the match, and Williams seemed to lose the rhythm on her serve a little bit too, getting broken early in the second set - but at the end of the day the No.1-ranked, No.1-seeded American still cruised in an hour and four minutes.
"I'm always happy to get to the next round," Williams said afterwards. "It doesn't matter who you play, it's always a really good win to go on and move on, so I'm happy I made it through the match."
The center court was packed - and Williams noticed. "It felt great," she said. "I definitely didn't expect that. I walked out and I felt honored. That's one of the reasons I love to play, to come to countries I've never been to and play in front of a packed stadium. It's just great. I really look at it as an honor.
"I could really feel a connection with the Swedish people. It was beautiful."
Williams is now 47-3 on the year, her only losses coming in the quarterfinals of the Australian Open (to Sloane Stephens), the finals of Doha (to Victoria Azarenka) and the fourth round of Wimbledon (to Sabine Lisicki). But Williams is still perfect on clay this year - she is 24-0 on the surface now.
"I've always loved the clay - maybe my results weren't always as good on it," Williams said. "But I always loved sliding and running on it. Maybe I didn't always love playing so consistently - that's something I'm doing a lot better at now, so I think that's why this has become a much better surface for me. And hardcourts are so slow these days, so this isn't such bad preparation for the summer."
Williams beat Tatishvili in their only previous meeting, which was just recently at Roland Garros.
The next-highest seed in action, No.3 seed Klara Zakopalova, had little trouble with Ellen Allgurin in her match, breaking serve seven times and taking 48 minutes to beat the Swedish wildcard, 61 61.
"It was a fast match, but it's really tough to play against somebody you don't know," Zakopalova said. "She's very young and talented, so I made sure I was solid from the first point until the last point. I tried to be aggressive and stay solid on my serve as well, and I'm very happy that I'm through now."
Next up for Zakopalova is Arantxa Parra Santonja, who won her first round match on Monday. And Parra Santonja may be trouble - the Spaniard has beaten the Czech in all three previous meetings.
"I know her well, she's the same age as me and we've played for a long time against each other," Zakopalova said. "I have to play every point against her because she's a very dangerous player."
Other winners were Mathilde Johansson, Teliana Pereira, Nina Bratchikova, Alexandra Dulgheru and Dutch qualifier Richel Hogenkamp. Pereira had by far the most dramatic win of the day, fighting off double match point serving at 2-5, 15-40 in the third set and beating Dinah Pfizenmaier, 36 62 75.