01 - Preheat oven to 350°F. Grease and flour a 9x13-inch baking dish thoroughly, ensuring all surfaces are coated to prevent sticking.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt until evenly distributed. Set aside.
03 - In a large mixing bowl, beat softened butter and granulated sugar with an electric mixer on medium-high speed until pale and fluffy, approximately 3 minutes.
04 - Add eggs one at a time, beating thoroughly after each addition until fully incorporated. Mix in vanilla extract until combined.
05 - Alternately add the flour mixture and buttermilk to the butter mixture, beginning and ending with the flour mixture. Mix on low speed until just combined, being careful not to overmix.
06 - Spread the batter evenly into the prepared baking dish, smoothing the top with a spatula to ensure uniform baking.
07 - Bake for 30-35 minutes, or until a wooden toothpick inserted into the center emerges clean or with only a few moist crumbs.
08 - Allow the cake to cool in the pan for 15 minutes before transferring to a wire rack to cool completely.
09 - Whisk together powdered sugar, 2 tablespoons milk, and vanilla extract until smooth and pourable. Add additional milk 1 teaspoon at a time if needed to achieve desired consistency.
10 - Drizzle the vanilla glaze evenly over the completely cooled cake. Allow glaze to set for 15-20 minutes before slicing and serving.