Preheat oven to 350 degrees F. Line a 12 muffin pan with cupcake liners.

CUPCAKES: In a medium bowl melt butter in microwave on medium powder. Whisk in sugar until dissolved. Whisk in egg, yogurt, milk, lemon juice and zest, and vanilla until completely blended.

In a large bowl whisk together flour, baking powder, baking soda, and salt. Slowly whisk in wet ingredients until no lumps remain. Divide batter equally among muffin tin. Bake until toothpick comes out clean, about 15-20 minutes. Allow to cool completely.

FROSTING: Once cupcakes are cool, if using a vanilla bean, slice vanilla bean open and scrap out inside seeds*. Beat softened butter on medium speed with a standmixer or electric mixer until smooth and creamy, about 3 minutes. Add powdered sugar, vanilla and a pinch of salt and beat on high until frosting is fluffy, about 1-3 minutes, scraping down sides when necessary.

Evenly divide frosting between cupcakes. Sprinkle with lemon zest and enjoy!