A bit embarrassed asking this, but... I'm trying to replace a leaking valve off my faucet assembly, but am unable to unscrew the faucet cap. Here is the faucet assembly - Taboret® widespread lavatory faucet - K-8211-4
When you go to product site check out the "for owners" tab and open the second installation and care guide. On page 2, it shows the handle itself unscrewing so you can replace the red or blue color rings. Start opening it up there and see if you can work your way down to screw 55431 which is holding down the rest of the faucet to the valve.
Upper handle assembly
Lower handle assembly