What is the commercial passenger aircraft top speed record?
"Speed" is not a singular term in aviation. There are many different ways to measure speed. See for example Why is there a difference between GPS Speed and Indicator speed? Most commercial jets cruise with a true airspeed in the range 400-500 knots and an indicated airspeed in the range 200-300 knots.

For the purpose of passenger transportation, ground speed is interesting since it is a determining factor in how long it takes to get from A to B. But do note that ground speed has relatively little to do with aircraft performance, since two identical aircraft could have vastly different ground speeds if one was flying in a headwind and the other in a tailwind.

According to groundspeedrecords.com, the fastest ground speed ever recorded for a commercial aircraft is the Concorde with a record of 1205 knots. This website relies on pilots snapping a picture and uploading it to the site as proof, so it is possible that that record has been broken without it being recorded.

Excluding the Concorde, which is no longer in service, the fastest record is a Boeing 747-400 recorded at 752 knots in 2010. At the time of reaching that speed, the aircraft had a 213 knot tailwind (probably flying in a jetstream).