1 cup sugar
1 cup lemon juice
2/3 cup heavy cream
1 teaspoon vanilla
1 1/2 cups flour
1 teaspoon baking powder
3/4 teaspoon baking soda
Preheat oven to 350°F. Grease 2 loaf pans, line with parchment paper and spray with nonstick cooking spray.
In a large mixing bowl, combine the water and sugar and whisk until sugar is dissolved and the mixture is slightly thickened.  Add the lemon juice and heavy cream.  Stir until smooth.
Add the flours, baking powder, baking soda and salt and whisk until well blended.  Mix in the remaining 1 1/2 cups flour, baking soda, and salt and mix until just combined.  Fold in the butter and sugar mixture until well blended.  Fold in the egg whites until just blended.
Fold in the lemon zest and vanilla extract.
Sift together the flour mixture, sugar, and lemon zest.  Place the batter in