Perfect Vanilla Sheet Cake

For the cake:
Preheat oven to 180ºC (350ºF or Gas 4). Butter or spray a 13×9-inch pan, and set aside.

Whisk together flour, baking powder, baking soda, and salt. Set aside.

Whisk eggs. Add sugar and whisk until combined. Add vanilla extract and vegetable oil, whisk until combined. Gradually mix in the dry ingredients, alternating with buttermilk.

Pour batter into prepared pan and spread out evenly. Bake 30–35 minutes, or until a toothpick inserted into the centre comes out clean. Allow to cool completely in the pan on a wire rack before frosting.

For the frosting:
Using a handheld or stand mixer, beat together butter and icing sugar on low speed until light and fluffy. On medium speed, beat in milk and vanilla extract until smooth and spreadable. Spread frosting over the top of the cooled cake, then slice and serve.