How do I access the RenderTarget from a Blendable?

I am trying to write a Blendable plugin to do some post processing on a scene. The “OverrideBlendableSettings” method, which is the only one I can override, is passed a FSceneView object. However, I do not find any way to access the actual RenderTarget that the SceneView renders into, so I cannot do much with it. Is there a way to work with the RenderTarget from a Blendable, or have I simply misunderstood what they are for?

Thanks,