Preheat the oven to 350 degrees. Spray 3 6 inch cake pans with non stick spray and line the bottoms with parchment paper.
In a medium bowl, whisk together the all purpose flour, baking powder, baking soda and salt. Then set aside the dry ingredients.
2 ¼ cups (281 g) all-purpose flour, spooned and leveled, 1 ½ teaspoon baking powder, ¼ teaspoon baking soda, ½ teaspoon salt
In a large mixing bowl, cream together the butter and granulated white sugar with an electric hand mixer on high speed until fluffy, about 3-4 minutes. (If using a stand mixer, use the paddle attachment.)
10 tablespoon (140 g) unsalted butter, softened, 1 ½ cups (300 g) granulated white sugar
Then add in the eggs and vanilla and mix on medium-high speed until smooth, pale in color and slightly fluffy, about 2-3 minutes. Scrape the sides of the bowl with a rubber spatula as needed.
3 large eggs, at room temperature, 1 ½ tablespoon vanilla
Alternate adding the flour mixture and the buttermilk to the butter mixture a little at a time, until each has been added completely. Mix on low then medium speed just until the batter is combined and smooth, scraping the sides of the bowl as necessary.
1 cup (240 ml) buttermilk, at room temperature
Evenly distribute the cake batter among the parchment paper lined cake pans.
Bake the cakes for 29-32 minutes, or until a toothpick comes out clean from the centers.
Let the cakes cool in the pans for 5 minutes, then transfer the cake layers to a wire rack to completely cool.