Render GUI Texture on RenderTexture

I'm trying to render GUI elements on a RenderTexture. One of my camera's target texture is assigned to this RenderTexture. I use the pointer of this texture to send to an OpenGL plugin. The problem is, I want my GUI elements to show up on this RenderTexture only (not in scene view or anywhere else), so that when I receive the texture in OpenGL the GUI elements baked into the texture. As far as I know, the GUI class can't render to a RenderTexture, is there some way to render a GUI Texture to a RenderTexture?