Plywood? Cement board? What exactly are you attempting to accomplish? Neither are an adequate surface for a counter top. If you are looking for a concrete top, I think you will end up with a huge mess as you are definitely over your head here.

I want to make sure I understand what you’re trying to accomplish. You want a plywood countertop that is heat and scratch resistant and that you can paint or coat with a finish that looks like concrete?

Jodie:

Respectfully, your ideas are terrible and I say that as a professional in the countertop business for over 40 years.

Perhaps you could tell us what look you're trying to accomplish, your budget, your skill level, and the tools you have and are familiar with so we could help.

NO NO NO If you want a concrete counter you get a pro who does those counters . Backer board is not a counter material and for sure not paintable for whatever reason you are thinking of.Paint is not heat , or scracth proof . Stop right now.

Go to a stone fabricator and look at pure white quartz. It will stain much less than any concrete.