Flourless Sponge Cake

1. Preheat oven to 325°F.

2. Whisk 1/4 cup vanilla sugar (or sugar), matzo cake meal and lemon zest in a medium bowl.

3. Beat egg whites, salt and lemon juice in a large bowl with an electric mixer on medium speed until frothy. Increase speed to high and beat until soft peaks form. Add remaining 3/4 cup vanilla sugar (or sugar) 1 Tbsp. at a time, beating until glossy and stiff peaks form.

4. Fold dry ingredients into beaten whites with a rubber spatula. (If using vanilla extract, add it now.) Scrape batter into an ungreased 10-inch angel food cake pan. Run a spatula in a circle through batter to release air bubbles; smooth the top.

5. Bake cake for 40 to 50 minutes, or until top springs back when touched lightly and a skewer inserted in the center comes out clean. (The top of the cake will be cracked.) Invert the cake to cool completely. (If the pan has no "legs," invert it over the neck of a glass bottle.)

6. With a knife, loosen edges of cake and invert onto a serving platter.

Tips: To make vanilla sugar, split 1 vanilla bean lengthwise with the tip of a sharp knife. Cut into 2-inch pieces and grind in a blender with 1 cup sugar. Pass sugar through a fine sieve. (The sugar will keep indefinitely in a tightly covered container at room temperature.)

To warm egg whites to room temperature, place them in a bowl over hot water. Whisk for a few minutes until they feel slightly warm to the touch.

Dried egg whites, such as Just Whites, reconstituted, can be substituted for fresh egg whites.