Preheat the oven to 350 degrees Fahrenheit. Spray two 8-inch cake pans with cooking spray and line the bottoms with parchment paper. Set aside.
Using a stand mixer or hand mixer and large mixing bowl, cream the butter and sugar until light and fluffy. Beat in the eggs one at a time, then add the vanilla extract.
In a separate bowl, whisk together the two flours, salt, baking powder and baking soda.
In two batches, alternate adding the dry mixture and buttermilk into the creamed butter and sugar mixture. Start with half of the dry ingredients, add in half of the buttermilk, then repeat, mixing well after each addition and scraping down the sides with a spatula as needed.
Divide the batter evenly among the two prepared cake pans, gently tapping the filled pans on the counter to get out any air bubbles.
Bake the cakes in the preheated 350-degree oven for 28-30 minutes, or until a cake tester inserted into the center of each one comes out clean. Let cool for 10-15 minutes, then turn the cakes out of their pans onto a cooling rack - removing the parchment paper on the bottom - to cool completely.
Once the cake layers are completely cool, use a serrated knife to level out the tops. This will help the layers sit nicely on one another without sliding after they're frosted.