Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large mixing bowl, combine flour, baking powder, baking soda, and salt. Whisk to blend.

In a separate bowl, cream the softened butter and granulated sugar together until light and fluffy.

Beat in the eggs one at a time, mixing in the orange zest and vanilla extract.

In another bowl, combine buttermilk and fresh orange juice. Alternate adding the dry mixture with the buttermilk mixture to the creamed butter and sugar until combined.

Divide the batter between the prepared pans and level the tops. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

Let the cakes cool in the pans for about 10 minutes before transferring to wire racks.

In a mixing bowl, beat the softened butter until creamy. Gradually add in powdered sugar, orange juice, and zest, mixing until smooth and fluffy.

Once the cakes are completely cooled, place one layer on a serving plate, spread frosting on top, place the second layer and frost the top and sides.