Place the butter into a glass measuring cup that is safe for the microwave and microwave it until it is completely melted.
Once the butter is melted, whisk in the light brown sugar and heavy cream. Microwave for 2 minutes.
After 2 minutes, stir with a whisk and then microwave for an additional 2-3 minutes. Carefully remove the container and allow the caramel sauce to cool until you can handle it.
Pour the cooled caramel sauce into a jar and refrigerate.
If you need the caramel sauce to be saucy, microwave for 20-30 seconds and serve.