How to loosen soft metal faucet assembly without scratching metal

[GoshenPlumber]

I need to remove the handle from my bathroom sink faucet in order to replace the ceramic disc cartridge. My problem -- I cannot figure our how to grip the faucet assembly with a wrench in order to loosen the assembly without scratching the soft metal.

This problem is best illustrated with the two attached pictures.

Any suggestions? Thank you.

 

[havasu]

Is there a nut on the underside which you could loosen, making the metal bell easier to remove?

 

[IFIXH20]

I usually use a rubber strap wrench, but if that do not work I loosen the nut under the sink as Havasu said.