Beat egg whites until stiff peaks are formed.
In another bowl beat the egg yolks until light and creamy, then mix in sugar. Add the flour, salt, lemon juice and vanilla and mix well.
Fold egg whites into the batter mixture and pour into a greased/floured 9-inch round pan.
For the topping, blend butter with sugar, nuts, cinnamon, flour, and cocoa, then sprinkle mixture on top of batter.
Bake at 325°F for 20 minutes, reduce heat to 350°F and bake for another 15 minutes.