Pre-heat oven to 300 degrees F.

Grease and flour cake pan.

In a large mixing bowl mix together sugar and butter, add each egg yolk one at time, mixing well after each addition until it is nice and creamy.

Add vanilla and sour cream.

Into a separate bowl, sift together the sifted flour, salt, and soda.

Add sifted dry ingredients to batter, in thirds, mixing well after each addition.

In a separate bowl, beat egg whites until stiff peaks form.

Gently fold egg whites into the cake batter by hand.

Pour batter into the greased and floured cake pan and bake for approximately 1.5 hours or until cake tests done with a toothpick.