In a medium saucepan, melt butter over medium heat. Cook until butter turns a medium-brown color and has a nutty aroma, about 10 minutes. Pour into a small bowl; let cool slightly. Refrigerate until almost firm, about 50 minutes, stirring occasionally.
In a large bowl, beat browned butter with a mixer at medium speed until creamy. Gradually add confectioners’ sugar, milk, cinnamon, and salt, beating until smooth.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/apple-spice-cake-with-browned-butter-frosting-recipe/