Melt 1 Tbsp butter in a nonstick pan over med/high heat. Add 1/4 cup light brown sugar and stir to combine. Add 2 Tbsp water, stir, and bring to a boil.
Cream 1 stick of butter and granulated sugar with an electric mixer on med/high speed until light and fluffy, about 2 minutes. Add the egg, blending well.