Preparation

1. Preheat your oven to 350°F and grease your pans.
2. In one bowl, whisk together the flour, baking powder, baking soda, and salt.
3. In another bowl, rub the sugar and orange zest together until fragrant.
4. Add the oil or butter to the sugar mixture, mix well, and then beat in the eggs one at a time.
5. Stir in the vanilla extract.
6. Alternate adding the dry mixture with buttermilk and orange juice in three rounds, mixing until just combined.

Baking

1. Pour the batter into prepared pans, tap them to release air bubbles, and bake until a toothpick comes out clean, about 22 to 28 minutes.

Frosting

1. For cream cheese frosting: Beat cream cheese and butter until smooth, add powdered sugar, vanilla, and orange zest. Thin with orange juice as necessary.
2. For vanilla buttercream: Beat butter until fluffy, add powdered sugar, cream or milk, vanilla, and orange extract if desired.

Assembly

1. Level the cooled cake layers if domed, spread a thin layer of frosting on the first layer, and stack the second layer.
2. Apply a crumb coat, chill for 15-20 minutes, and then frost with the final layer.