I would guess that everybody knows this method but just in case you don’t or are new to the microwave world (you never know, perhaps you previously lived in a log cabin with no electricity!)
Being a baker, when we got our first microwave, this was sooo easy with hardly any fuss at all!
Place butter in a microwaveable bowl; cover with a piece of wax paper. Microwave in 30 second increments on level 3 until completely melted. Cool slightly, measure & use in your recipe.