Preheat oven to 350F/175C and grease a 9x13 inch pan.
In a small mixing bowl, add the wet ingredients and mix well to combine.
In a separate bowl, mix together the dry ingredients.
Pour the wet ingredients into the bowl with the dry and mix until just combined.
Pour into the prepared pan and bake 40 minutes or until a cake tester comes out clean.
Baking Times For Different Pan Sizes: For two 8-inch round pans, bake 30-35 minutes. For two 9-inch round pans, bake 25-30 minutes. For 24-36 cupcakes, 15-20 minutes
Follow the recipe closely. I know you'll be tempted to throw everything in the bowl and mix, but mixing the wet and dry ingredients separately before combining them helps prevent over mixing, which will ruin the cake texture.
Use room temperature ingredients. Cake batter mixes evenly when all the ingredients are about the same temperature. Set out your ingredients 1 hour before beginning and allow the melted butter to cool before using it.
If you don't have buttermilk, you can make your own by adding one teaspoon of white vinegar or lemon juice to 3/4 cups of milk. Stir and let sit for 5 minutes. The mixture may be a little curdled, but that's just fine.
For homemade buttermilk, full-fat milk works best to produce a moister cake. That said, low-fat milk will work too.
Cool cake completely before frosting. Frosting a warm cake will melt the frosting.