Prepare pans and oven
Preheat the oven to 175°C / 350°F and grease and line your 6 inch cake tins.
Mix dry ingredients
In a bowl, whisk together the flour, baking powder, and salt until evenly combined.
Cream butter and sugar
In a separate large bowl, beat the butter and sugar together for 3–4 minutes until very light and fluffy.
Add eggs and vanilla
Beat in the eggs one at a time, mixing well after each addition, then mix in the vanilla until smooth.
Add dry ingredients and milk
Add about half of the dry ingredients and mix on low just until combined, then pour in about half of the milk and mix again. Repeat with the remaining dry ingredients and milk, mixing only until the batter is smooth with no streaks of flour.
Bake the layers
Divide the batter evenly between the prepared 6 inch tins, level the tops, and bake for about 25–35 minutes, or until the centers spring back and a skewer comes out clean.
Cool completely
Let the cakes cool in the tins for 10–15 minutes, then turn out onto a wire rack and cool completely before filling and frosting.