Grind almonds in a food processor with 1 tablespoon of sugar and sugar substitute. Set aside.
In a medium-sized bowl, beat egg yolks, 1 tablespoon sugar, 1/2 of the sugar substitute, lemon rind, cinnamon, vanilla extract, baking soda, oil, and salt until light-colored and thick. Stir in almond mixture.
In a separate bowl, beat egg whites until soft peaks form. Gradually add vinegar or lemon juice and remaining sugar and sugar substitute, beating until stiff but not dry. Very carefully fold beaten egg whites into almond mixture until combined.
Transfer batter to a long loaf pan, which has been lined with wax paper and greased. Bake at 375 degrees F for about 35 minutes, or until tester comes out clean.
Cool and turn out onto a plate. Remove wax paper. If desired, top with sugar-free gelatin. Cut into bars.