How to clean stains from anodized aluminum pans?
This looks like you are starting to getting a layer of polymerized oil on the pan, like the seasoning on a cast iron pan. 

I wouldn't try removing it. The usual methods are either using a strong base (which works really well) or mechanical forms of removal, which are less effective. But the strong base will corrode your pan, and the mechanical removal will scratch and damage the anodized layer. 

You can try the baking soda, but it is so weak a base that it is unlikely to have much of an effect. 

I would just continue to use the pan as it is.