Just to be clear, there has never been a Mac CPU. The Mac difference is an Apple operating system that is a derivative of Linux, and some proprietary hardware interfaces to other hardware. There were Motorola CPU's for a long time, but for years now Apple has been using Intel CPU's, which is why Bootcamp, which is primarily a collection of drivers for the proprietary stuff on Mac motherboards, allows you to run Windows on the same machines.
You are going to make music software for Windows only by writing it to run under Windows, just as you would make it for Mac only by writing it to run on OSX whatever. Cakewalk has been doing that for decades, and so far as I know anyone who is writing it to work on both systems natively is writing two different versions/systems. You can of course use a single Windows version of Cakewalk on both a PC and Mac running Bootcamp.
If you have gotten your Sonar project version to the point where the tracks are rendered to final audio files, then they can be exported and will open on any system capable of audio editing. If you are still at the stage where you are using effects and plugins that you are not ready to commit to a final audio file, then you would have trouble even if your collaborator were using Sonar. Unless he has your exact versions of plugins loaded on his computer, your project will not run on his system whether it is Windows Cakewalk, OSX ProTools, Linux Ardour or whatever. If he is going to be using his own plugins on your project find out how he wants you to send him your stuff. It is relatively easy to apply new effects to dry audio, and nearly impossible to remove effects from audio that has been processed.