My solution came from the French! A butter keeper uses ancient food preservation techniques to keep butter soft, but not rancid. I recently bought one on-line (using my Amazon Prime account and paid no shipping) for $11.95. The process is simple. Set a 1/2 stick of butter on the counter. Once at room temperature smash it into the inverted cup. Add 1/3 cup water to the canister. Put the lit on and a seal keeps the butter at room temperature.
Here is a photo. I'm holding the lid. It is placed, downward facing, on the canister. You can just make out the word butter, written in blue.
Image credit: Author, M. Gustafson Gervasi, 2012
Our only problem is that we keep our house so cold, the butter at room temperature is not that soft!