Preheat the oven to 325 degrees F. Spray three 8-inch cake pans with non-stick spray, line with parchment paper, and spray again. Set aside.
In a medium bowl, whisk together the cake flour, baking powder and salt. Set aside.
Using a stand mixer fitted with the paddle attachment, beat the butter, sugar, and canola oil on medium-high speed until light and fluffy, about 3 to 5 minutes.
Add the eggs and egg yolks, in a few additions, beating well and scraping down the sides of the bowl between each addition. Add the vanilla and butter extracts. Continue to beat for 2 to 3 minutes on medium-high speed.
With the mixer on low speed, alternately add the flour mixture and the sour cream in three additions, starting and ending with the flour mixture. Mix on low, just until flour is combined.
Bake for 25 to 30 minutes, or until a toothpick inserted in the center of the cake comes out with a few moist crumbs on it.
Let cool completely before using.