How do you remove soldermask from a Trace (RF Track) ?

There is a free app available from the EMA App store that will do this for you. Check out:- Download the GraserWare ClineRouteKeepout App - OrCAD Software Apps and Extensions | EMA Store (ema-eda.com)

There is a free app available from the EMA App store that will do this for you. Check out:- Download the GraserWare ClineRouteKeepout App - OrCAD Software Apps and Extensions | EMA Store (ema-eda.com)

Is there a tutorial on how to use it ?

Its should be self explanatory, invoke the command, select the track you want to add the keepout to and fill in the form (PDF attached). I would add that this only creates a routekeepout, you would then need to copy that to the soldermask_top or _bottom layer. ClineToRouteKeepout_help.pdf

Steve, does it put a soldermask dam between the component pads and the trace?  Looking at the pictures, it doesn't look like it does.  Here is what I normally do to make the contract mfg happy.  If I remove the gap, they always complain

No it simply copies the cline path to a route keepout area on a lyer defined by the user, increased by a defined amount.