I'm trying to change a cartridge in a Moen bathroom faucet (2 handled chateau style, see picture below). the problem is that I cannot even remove the top cap to remove the handle. they say use a screwdriver or sharp instrument. It doesn't work. I keep scratching the cap. And suggestions?

https://www.amazon.com/Moen-4920-Cha.../dp/B000TFD6C0