Position oven rack to the lowest setting, and remove middle rack. Preheat oven to 425°.
To prepare the soufflés, lightly coat 8 (8-ounce) soufflé dishes with cooking spray. Sprinkle evenly with 2 tablespoons sugar. Set aside.
Combine 1/2 cup sugar, 2 tablespoons flour, and 1/8 teaspoon salt in a heavy saucepan over medium heat, stirring with a whisk. Gradually add reduced-fat milk, stirring well with a whisk; bring to a boil. Cook 1 minute or until thick and bubbly, stirring constantly. Remove from heat. Add butter; stir well. Transfer mixture to a large bowl; cool to room temperature. Add rind, juice, and egg yolks; stir until blended.
Place egg whites in a large mixing bowl; beat at high speed with a mixer until soft peaks form. Add remaining 1/4 cup sugar, 1 tablespoon at a time, beating until stiff peaks form (do not overbeat). Gently fold one-fourth of egg white mixture into lemon mixture, and gently fold in remaining egg white mixture. Gently spoon mixture into prepared dishes. Sharply tap dishes 2 or 3 times on counter to level. Place dishes on a baking sheet; place baking sheet on the bottom rack of 425° oven. Immediately reduce oven temperature to 350° (do not remove soufflés from oven). Bake 40 minutes or until a wooden pick inserted in the side of soufflé comes out clean.
To prepare sauce, combine 1/4 cup sugar, 2 tablespoons flour, and 1/8 teaspoon salt in a small saucepan over medium-low heat. Combine low-fat buttermilk and egg, stirring well with a whisk. Gradually add buttermilk mixture to pan, stirring constantly with a whisk. Cook mixture for 10 minutes or until a thermometer registers 160°, stirring constantly with a whisk. Serve sauce with soufflés.