If a recipe for baking calls for just "butter" is it salted or unsalted?
Most of the time baking recipes want unsalted butter. In addition to salt, salted butter almost always has more water than unsalted which will affect the texture of your finished product.
I would use unsalted, but taste before completing and maybe add a pinch or 2 of salt.
If no added salt is mentioned in the recipe I would use salted. Everything needs a smidge.