Preheat oven to 350 degrees

In a stand mixer with the paddle attachment, cream together the butter and sugar until light and fluffy

In a medium bowl, whisk together flour, salt and baking powder

Add eggs, vanilla and lemon zest and beat well

Add in the flour and milk, alternating between and ending with the flour

Mix the cake batter until well combined

Fold in blueberries

Pour the batter into a greased or parchment paper lined square 8" inch pan

Bake at 350 for 30 minutes or until the top is golden brown and a toothpick comes out clean from the center

Let cool on a wire rack for 30 minutes before frosting

FROSTING

In the stand of a mixer, beat the butter until light and creamy (about 2-3 minutes)

Gradually add the powdered sugar, one cup at a time, beating slowly until the sugar is fully incorporated. After each addition, increase the speed to medium and beat until the mixture is smooth and creamy. Scrape down the sides of the bowl as needed.

Add the vanilla extract and 1-2 tablespoons of milk the mixture. Beat on medium speed for about 1 minute. If the frosting is too thick, add more milk or cream, one tablespoon at a time, until you reach the desired consistency.