Not a great idea! It's razor scraper time. Cement board (cbu) does two things, it provides a good surface to tile on, and when installed properly (nailing it down to a concrete slab is not one of them!) has a layer of thinset underneath it filling in any imperfections, providing 100% support.
The best place for tiling info that is sound and will provide something that lasts is www.johnbridge.com.