Preheat the oven to 350 degrees.
Prepare 3 9" round baking pans with non-stick baking spray and put aside.
In the bowl of your mixer, beat butter, vegetable oil, salt and sugar on high until fluffy and smooth (about 5 minutes).
Next, add eggs one at a time to the bowl and beat on medium until well incorporated.
In a separate large bowl, sift cake flour, baking powder and baking soda together.
Turn the mixer to low and add half of flour mixture to the mixer and fully incorporate.
Next add sour cream to mixer and blend well and lastly finish with remaining flour mixture and mix well.
Finally add vanilla extract and butter extract to mixer and finish beating on low until everything is well mixed.
Make sure to scrap the bottom of the bowl as well.
Evenly add cake mixture into prepared baking pans and place in oven to bake for 25-30 minutes or until a toothpick inserted into the center of the cake comes out clean but don't overbake (crucial not to overbake this cake)!!
Remove cakes and oven and rest in pans for 10 minutes.
Next remove layers from pans and place on cooling racks for one hour.
Wrap each layer in plastic wrap and place in the freezer for 1 hour to make it easier to work with when assembling the cake.