Preheat your oven to 325 degrees F. Spray two 8-inch round cake pans with nonstick spray, line the bottom with parchment paper, spray again and set aside.
In a medium sized mixing bowl, whisk together the cake flour, baking powder and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter, sugar and zest on medium-high speed until light and fluffy, about two minutes.
Add the eggs, one at a time, making sure to scrape down the sides and bottom of the bowl between each addition.
With the mixer on low speed, alternately add the dry ingredients with the buttermilk and orange juice, starting and ending with the flour mixture. Mix just until the dry ingredients are incorporated.
Bake the cake layers for 20 to 23 minutes, or until a toothpick inserted in the center of the cake comes out with a few moist crumbs on it. Let the cakes cool in their pans for about 10 minutes and then invert them on to wire racks to cool completely.TIP: spray your wire racks with nonstick cooking spray.