• ½ pound unsalted butter, softened
• ½ cup plus 2 tablespoons fine cornmeal
• 1 teaspoon finely grated lemon zest
• 1½ teaspoons fresh rosemary leaves, finely chopped
• 1 cup sugar
• 4 eggs, separated
• 1½ teaspoons rose water
• ½ teaspoon pure vanilla extract
• ½ teaspoon cream of tartar
• ¼ teaspoon baking soda
• ½ cup sour cream
• 1 cup sifted cake flour
• ¼ teaspoon salt

Preheat the oven to 325 degrees. Use one tablespoon of the butter to butter a 9-inch loaf pan and dust with 2 tablespoons of the cornmeal. Shake out the pan.

Beat the remaining butter, lemon zest, rosemary, and sugar in a bowl until light and fluffy, about 10 minutes. Beat in the egg yolks one at a time. Add the rose water, vanilla, cream of tartar, baking soda, and sour cream and mix well. Sift the remaining cup of cornmeal together with the flour and salt, and add the mixture to the batter. Mix until just incorporated.

Whip the egg whites until stiff but not dry and fold into the batter.

Bake until a thin skewer stuck in the center of the cake comes out clean, 50 to 60 minutes. Cool on a rack for 15 minutes and then unmold the cake.