Should I use salted or unsalted butter if the recipe doesn't specify?
Unsalted for sure! You can always add salt, can't take it back out though ...
Unsalted for Baking, otherwise I usually use salted because that's what I have more often.
I don't remember the last time I bought salted butter. I use unsalted for everything so that I have control over the salt content.
Use what you have around.
unsalted, if you have it on hand.
You can use either in baking. Lately, I'm finding I like baking with salted butter better. It only adds a negledgeble amount of salt. Recipes from older cookbooks where the type of butter isn't specified or they give you a choice of butter or margarine, used salted butter because margarine has salt, so the recipe has taken the salt in it into consideration.
Sweet (unsalted) always unless recipe specifically asks for salted. You can always add salt.
You should use unsalted, but If you only have salted, subtract 1/4 tsp salt from the recipe or it will be too salty