The eight-time European champions moved onto 10 points from four matches in the 18-team league phase, one point above holders Barcelona, who will bid to maintain their 100% record when they welcome 2025 winners Arsenal to the Camp Nou on Thursday.
Lyon dominated early on but had to wait until the 31st minute to take the lead, when farcical Juve defending and ponderous goalkeeping from Danielle de Jong allowed Katoto to hook in a close-range volley.
Katoto doubled the advantage just four minutes later with a cool finish after some neat footwork, scoring for the seventh time in the competition this season.
Melchie Dumornay pounced on another defensive error to make it three before half-time.
Teenager Lily Yohannes scored with 10 minutes remaining, and there was still time for her fellow American Korbin Shrader and Wendie Renard - via a rebound after De Jong saved her weak attempted Panenka penalty - to complete the rout.
Lyon have yet to concede in the league phase, while Juve remain eighth in the table with six points.
Danish side Koge climbed above Inter Milan and Roma into 10th place as Simone Boye's 82nd-minute strike salvaged a 1-1 draw at second-bottom Leuven in Belgium.
Benfica's game against Austria Vienna in Lisbon was postponed until Thursday due to the effects of Storm Charles.