No, that is the nut for one of the pulleys. The cover almost gets welded on, from the heat. Carefully try to pry it off,without ruining the gasket. Mine does not have that filter, but it looks like it should be cleaned. Maybe try to give the cover a few gentle taps, with a rubber mallet and try to wiggle it free. I'm sure you get some more suggestions.
Rich
Sent from my iPad using Tapatalk