New York (24-6) has won six games in a row and 10 of its past 11.
Stewart, who scored 45 points in a 90-73 win over the Fever on May 21 and had a 43-point performance against the Phoenix Mercury on July 5, became the first player in WNBA history to score at least 40 points three times in the same season. She joins Diana Taurasi (four times) and Maya Moore (three) as the only players to top the 40-point plateau three times in their career.
Stewart also had six rebounds and six assists, becoming the first player league history with multiple games of 40 points, 5 rebounds and 5 assists in a season, according to ESPN Stats & Information.
"I was getting some good looks," Stewart said. "They were switching a lot, just continuing to read what the defense gave me. And that kind of just continued throughout [the game]. I'm really happy with how we all played, in general."
Ionescu hit two 3-pointers, giving her 101 made 3s this year to join Taurasi and Kelsey Plum as the only players in league history with 100-plus 3s in a single season.
The Associated Press contributed to this report.