Preheat oven to 350F and grease 9x13 pan.

In a large bowl, using a hand mixer or stand mixer, beat butter and sugar until creamy. Add in eggs, vanilla, and lemon zest and beat until smooth.

In a separate bowl, whisk together flour, baking soda, baking powder, and salt.

Slowly add dry ingredients to wet and using mixer, mix until all combined.

Pour batter into greased dish and press into corners, flattening with spatula to make even.

Bake for 25-30 minutes or until slightly golden. Let cool.

While cooling, use a mixer to blend together frosting ingredients, starting with butter, cream cheese, and vanilla. Slowly blend in powdered sugar, milk, and salt. Once creamy, spread over cooled cookie bars. Decorate with sprinkles. Cut into bars.