What I did was:
select ramp face -> Extrude (E) -> constraint to one of the horizontal axes (Y for me, x/y for you, depends where the pyramid is facing) -> snap to edge, click, and done.
Depending where your ramp began, you might also need to move/merge/extrude/etc on the top side, so it’s continuous between the very top ramp and the bottom. That’s what I also had to do (my initial ramp began from the 2nd on top, but then I was like “that makes no sense, unless there’s a door or something”).
Behold the might of the Mayans. I’m not saying aliens, but…