Preheat the oven to 300° F. Grease and flour a bundt cake pan.
Using a stand mixer or a hand mixer, cream the butter and the sugar at medium speed. Next, add the egg yolks and vanilla and continue to mix until light and fluffy.
Whisk together the flour, salt and the baking soda together in a bowl. Add to sugar and butter mixture a little at a time. Next, add the sour cream and mix until combined.
SPARKLE NOTE! THE NEXT STEP IS WHERE THE MAGIC HAPPENS FOR A LOVELY CRUSTY TOP! AVOID OVER FOLDING AND ADD THE FLUFFY EGG WHITES ALL AT ONCE!
In a separate mixing bowl, beat the egg whites to stiff peaks. Immediately add the fluffy egg whites into the batter all at one time. Tilting a large rubber spatula fold the egg whites in using no more than five or six strokes. BE CAREFUL NOT TO OVER FOLD!
Pour the Old Fashioned Melt In Your Mouth Sour Cream Pound Cake batter into the prepared bundt pan.
Bake for 1 1/2 hours. Insert a skewer into the hot cake and pull out gently. It is done if it comes out clean. Continue baking until the skewer comes out clean. Remove the Old Fashioned Melt In Your Mouth Sour Cream Pound Cake from the oven and place on a cooling rack for 15 minutes. Invert the cake onto a pretty cake stand or cake plate.