I really don't know what I'm doing wrong, but I haven't been able to do a simple Bake for a day. In this example I have 2 materials on the same object. I mapped with UV mapping, copied the object, and applied the material to the copied object, making the copied object diffuse the bake result of the first object.
Obviously I inserted a "Bake Diffuse" image in all 2 materials on which I have to bake with the relative selected nodes, as per practice.
The result I get, however, is strange.
I am using Blender 3.0.1
I leave the original file for sharing here: Bake Test.blend