- In a bowl, cream butter.
- Gradually beat in sugar until light and fluffy, about 5-7 minutes.
- Add egg yolks, one at a time, beating well after each addition.
- Combine flour, baking soda, and salt; add to creamed mixture alternately with sour cream and vanilla.
- Beat on low just until blended.
- Beat egg whites in separate bowl on high until stiff peaks form.
- Fold egg whites into cake batter until blended.
- Spray baking oil in desired pan and sprinkle with sugar and cinnamon (nuts optional).
- Pour cake batter into pan or fill with spoonfuls of batter until evenly spread.
- Bake at 325 °F for 1 hour and 25 minutes or until toothpick inserted in the middle comes out clean.
- Cool in pan 15 minutes.
- Slightly toss cake in pan to loosen edges then turn cake over onto plate and cool completely.
- Optional icing: combine confectioners' sugar, water (1 teaspoonful at a time), and lemon juice or extract.
- Stir until desired consistency—adding more water (1 teaspoon at a time).
- Pour by spoon over cake, if desired.