Sift thoroughly 1/4 cup sugar, flour, and salt; set aside.
Beat egg whites until foamy. Add lemon juice, and beat until soft peaks form. Gradually sprinkle remaining 1 cup sugar onto whites, beating at medium speed.
Sift 1/4 cup flour mixture over whites, and gently fold in by hand, with fingers spread. Add vanilla and orange rind. Fold in remaining flour mixture, alternating with grated chocolate.
Pour into clean, dry tube pan. (Do not grease pan or use a nonstick pan, as the batter will not rise.) Cut through batter with knife to remove air bubbles.
Bake at 350° for 40 to 45 minutes or until cake springs back when lightly touched.
Invert pan and cool 30 to 45 minutes. Gently loosen cake from sides of pan, using a narrow metal spatula; remove cake from pan.
Serve with strawberries and lightly sweetened whipped cream flavored with small amount of vanilla, to taste.
*Leave eggs out of refrigerator for about 15 minutes.
**Nell recommends Madagascar Bourbon Pur Vanilla Extract by Nielsen-Massey Vanillas.
***You can use 3 (1.2-ounce) Newman's Own Organics Sweet Dark Orange Dark Chocolate bars; the slightly less amount of chocolate is negligible. You also may substitute other brands of orange-dark chocolate bars, if desired.