Preheat your oven to 350 degrees F. Spray three 8-inch or four 6-inch round cake pans with cooking spray, then place parchment rounds on the bottom and spray again. Set aside.

In a medium size bowl, whisk together the cake flour, baking powder, and salt. Set aside.

In a stand mixer fitted with the paddle attachment, beat the butter, Jell-O, and sugar for about 2 to 3 minutes, until light and fluffy. 

With the mixer on medium speed, gradually add the egg whites, making sure to scrape down the sides of the bowl between each addition. 

Add the sour cream and vanilla. Mix for another 2 minutes on medium speed. Scrape down the bottom and sides of the bowl.

With the mixer on low speed, alternately add the flour mixture and the buttermilk, starting and ending with the flour mixture. Mix until combined. Scrape down the sides of the bowl and mix again on low for another 20 seconds.

Divide the batter evenly between the prepared pans (about 16 ounces of batter in each pan). I used three 8-inch pans and my cooking time was 22 minutes. Baking time should be between 22-25 minutes for the 8-inch, but make sure to check on your cakes around 22 minutes, inserting a toothpick into the top of the cake (should come out with just a few crumbs) or gently tapping the top of your cake (shouldn't jiggle, but instead, bounce back up when done).

Let cool in your pans for 10 minutes and then invert onto wire cooling racks until completely cooled.

For the Cream Cheese Frosting

In a stand mixer fitted with the paddle attachment, combine the butter and cream cheese and beat on medium speed until smooth, about 1 minute.

With the mixer on low, gradually add the powdered sugar, one cup at a time, until incorporated. 

Keeping the mixer on low, add the cream, vanilla and salt.

Turn the mixer to medium and beat the frosting for 3-5 minutes, or until it is light in color (almost white) and texture.

To remove air bubbles from the frosting, use a wooden spoon to stir and push out the air bubbles.