Hello. What kind of kitchen tool do use ideally to cut a lemon? Thank you.

Your knife needs to be extremely sharp. Most people think a "sharpening steel" sharpens the blade. It simply "hones" the blade, straightening it. You need a knife sharpener. Or better, a service that will do it for you (there used to be this old guy in the "knife truck" that drove around Brooklyn Hgts, I miss him). A hack I use (arthritic hands) is to pierce the rind so your blade has an entry point, that will make the slicing easier.

Mostly hand and eye coordination, a sharp knife and practice, practice, practice.

Irina,
Have you tried sharpening your knife?

I use a regular steel chefs knife.