Preheat oven to 300 degrees.
Grease and flour a bundt pan
Cream butter and sugar with paddle
Add egg yolks (one at a time)
Add flour and soda slowly, alternating between that and sour cream.
Beat well - it is a THICK batter.
In another bowl, beat egg whites stiff with sugar.
Fold egg whites into batter
Pour 1/2 to 2/3 of batter in the pan.
Sprinkle half of the sugar mixture in the center.
Top with remaining batter.
Sprinkle with remaining sugar mixture on top.
Bake for 85-90 min.
Cake is done with a toothpick comes out clean. (Better underbaked than over!)
Let cake sit for 10 minutes
Flip over and cool on a cooling rack