Preheat the oven to 350 degrees. Prepare 1 9" round baking pan at least 2 inches high on the sides with non-stick baking spray and put aside.
In the clean bowl of your stand mixer, beat butter, vegetable oil, salt and sugar on high until fluffy and smooth (about 4 minutes).
Next, add eggs one at a time to the bowl and beat on medium until well incorporated. In a separate large bowl, sift flour and baking powder 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 to mixer and finish beating on low until everything is well mixed. Make sure to scrape the sides of the bowl.
Add cake batter to prepared baking pan and bake for 33-38 minutes or until a toothpick inserted into the center comes out clean.
Remove cake from oven and rest in pan for 10 minutes. Then remove layer from pan and place on cooling rack for 30 minutes.
Wrap the layer in plastic wrap and place in the refrigerator for 1 hour to make it easier to work with when assembling the cake.