With the Rake plugin installed, a rake build step appears in the list of build steps. However, when also using the promoted builds plugin, the list of
actions to be executed with a promoted build does not contain the rake build step.

Upon investigation, the list of possible actions in the promoted builds plugin gets compiled using the following condition:

BuildStepDescriptor bsd = (BuildStepDescriptor) d;
                if(bsd.isApplicable(PromotionProcess.class))
                    list.add(d);

(in promoted-builds-plugin/src/main/java/hudson/plugins/promoted_builds/PromotionProcess.java)

I guess the reason why the Rake builder does not appear in the list of actions, is because the RakeDescriptor class
extends the Descriptor<Builder> class instead of the BuildStepDescriptor<Builder> class:

public static final class RakeDescriptor extends Descriptor<Builder> {

(in rake-plugin/src/main/java/hudson/plugins/rake/Rake.java)

My guess is that adding an

import hudson.tasks.BuildStepDescriptor;

and changing the RakeDescriptor class to:

public static final class RakeDescriptor extends BuildStepDescriptor<Builder> {

might fix this.

I have to say I am a complete Java newbie, and the Jenkins code is unknown to me, so
I might be way off.