Preheat your oven to 325 degrees F. Spray three 8-inch pans (or four 6-inch pans) with nonstick spray, line the bottoms with parchment paper and spray again. Set aside.
In a medium sized mixing bowl, whisk together the flour, baking powder, and salt. Set aside.
In the bowl of an electric mixer, fitted with the paddle attachment, beat the butter, sugar and Jell-O on medium-high speed for about 3 to 5 minutes. You want the mixture to get lighter in color and texture. Make sure to scrape the sides and bottom of the bowl to ensure all of the mixture has combined well.
With the mixer on medium speed, add the egg whites in three additions, making sure to scrape down the sides and bottom of the bowl between each addition. Once all of the egg whites are added, turn the mixer to medium-high and beat for about 2 to 3 minutes.
Add the sour cream and the orange extract. Don't worry if the mixture looks a little curdled. It will come back together when you add the flour mixture and buttermilk.
With the mixer on low speed, alternately add the flour mixture and the buttermilk, starting and ending with the flour mixture. Mix only until combined.
Divide the batter between the three 8-inch pans, about 22 ounces of batter in each pan. Bake on the middle rack for about 30 to 35 minutes, or until a toothpick inserted in the center of the cake comes out with a few moist crumbs on it.
Let the cakes cool on write racks, in the pans, for about 15 minutes and then invert onto wire racks to cool completely. TIP: spray your write racks with nonstick spray.