To prepare a vanilla layer cake with strawberries, you'll first need to prepare the cake batter. You can use store-bought vanilla cake mix, or you can make your own. Place the flour, baking powder, sugar, and salt into the bowl of your stand mixer and mix on medium speed until the ingredients are well combined. Add the buttermilk and beat the mixture until it's light and fluffy, about 2 minutes. Then add the eggs and vanilla extract, beating well after each addition. Pour the batter into your prepared cake pan and bake in the oven for 35 to 40 minutes or until toothpick inserted in center comes out clean. Let cake cool in pan for 10 minutes before removing to wire rack to cool completely.