Pre-heat the oven to 350°F (175°C). Grease, flour, and line the bottoms of three 8-inch cake pans with parchment and set aside.
Sift together the flour, baking powder, and salt and set aside. In a separate bowl, stir together the buttermilk and orange juice. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed for 2 minutes. Meanwhile, rub the sugar and orange zest together in a small bowl between your fingertips until fragrant. Add the sugar mixture to the butter and mix on medium-high until light and fluffy, 3 to 5 minutes. Stop the mixer and scrape down the bowl.
Turn the mixer to medium-low and add the vanilla and eggs, one at a time. Mix until combined. Stop the mixer and scrape down the bowl.
Turn the mixer to low and add the flour mixture in three batches, alternating with the orange juice mixture, beginning and ending with the flour mixture. Mix on medium for no more than 30 seconds after the last streaks of the flour mixture are combined.
Evenly divide the batter among the prepared pans. Bake for 23 to 26 minutes, or until a toothpick inserted into the center of the cakes comes out clean. Let them cool on a wire rack for 10 to 20 minutes before removing the cakes from their pans. Once the cakes have completely cooled, discard the parchment and level the tops of the cakes as needed.