Preheat oven to 350F/175C and grease a 9×13 inch pan (see recipe notes for more pan sizes)
Melt the butter (in a microwave in short intervals so as not to boil it), set aside to cool.
In a large mixing bowl, mix the flour, sugar, baking powder, baking soda and salt.
In a separate small mixing bowl, add the wet ingredients and mix well to combine.
Pour the wet ingredients into the bowl with the dry and mix until just combined.
Pour the batter into the prepared pan and bake 40 minutes or until a cake tester comes out clean.
Allow to cool and decorate with the frosting of your choice.
Notes
Baking Times For Different Pan Sizes: For two 8-inch round pans, 30-35 minutes. For two 9-inch round pans, 25-30 minutes. For 24-36 cupcakes, 15-20 minutes
For a bundt cake 35-40 minutes
It’s always best to use room-temperature ingredients. Cake batter mixes more evenly when all the ingredients are of a similar temperature. Set your ingredients out around 1 hour before you make the cake and allow the melted butter to cool slightly before using it.
For homemade buttermilk, full-fat milk works best, it produces more moist cake. That said, low-fat milk works too.
Cool the cake completely before frosting. If you frost a warm cake it will cause the frosting to become runny.