1. In a small bowl, with a fork, beat egg whites until slightly frothy, then measure and reserve exactly 1/3 cup; discard any remaining.
2. In a food processor, whirl almond paste, granulated sugar, and lemon peel until fine crumbs form. Add measured egg whites and whirl until very smooth.
3. Spoon mixture in 1-teaspoon portions, 2 inches apart, onto three buttered and floured or cooking parchment- lined 12- by 15-inch baking sheets. (Or spoon mixture into a pastry bag fitted with a 1/2-inch plain tip and squeeze 1 1/4-inch-wide rounds onto baking sheets.)
4. Sift powdered sugar over rounds to coat evenly. Let unbaked cookies stand, uncovered, until they develop a slight crust, about 4 hours.
5. Pinch top of each round with thumb and forefinger of both hands simultaneously to crinkle cookies.
6. Bake in a 350° oven until macaroons are a rich golden brown, 8 to 12 minutes. Cool cookies completely on sheets. Slide a thin spatula under cookies to release.
Note: Nutritional analysis is per cookie.