Melt the butter and remove from heat and set aside.
Add remaining ingredients to a cup that an immersion blender (also called stick blender, wand blender, hand blender) fits into or a blender and blend at high speed until a pale yellow.
Slowly add the melted butter until fully incorporated and thick on Low speed.
The result should be a creamy sauce. Season to taste. Scrape the sides of the cup/blender and pour into a serving dish. Serve immediately.