Plane passenger films weird rectangular glow above the clouds in Kazakhstan

During a flight from the city Almaty to Petropavlovsk in Kazakhstan on December 23, 2019, a passenger noticed a strange rectangular glow above the clouds on which he decided to film it.

It is unclear what the strange glow could have been but it is quite possible that it was a tall building sticking out of the cloud formation.

The tallest building in Kazakhstan is Emerald Towers 1 in Nu-Sultan which is 240 meters high, the Esentai Tower in Almaty is 200 meters high. The construction of both towers as well as other tall buildings are similar to the rectangular glow.

Image left: Esentai Tower - Image right: Emerald Towers 1 in Kazakhstan

The exact location, the altitude of the plane as well as the altitude level of the cloud formation at the moment the passenger noticed the glow is unknown but could it be that he has filmed the roof of a tall building reflected by the sunset or was it something else?