Toilet flange help???

Should the toilet flange sit on top of the ceramic tile or on top of the backerboard? If I raise the flange too high I am afraid that I might not have to much more than an inch to glue. What do you guys think?

Ideally, the flange sits on top of the finished flooring. You'll be okay if it is solid on the cbu. If you can cut out the pipe from below and add a new piece, it would be better. My unprofessional opinion.