Prepare a 9 inch cake pan or spring form pan: grease bottom and sides well.
Cut out a circle of wax paper and fit it into the bottom of the pan. Grease the paper.
Coat the bottom and sides of the pan with almond flour, shaking out the excess.
Beat egg yolks, zest, cinnamon, and 2 Tbsp sugar with electric mixer.
Mix almond flour with 2 Tbsp sugar and stir into the mixture above.
Beat egg whites, pinch of salt, and 4 Tbsp sugar until soft peaks form.
Blend a large spoonful of the egg white mixture into the almond mixture with a spatula. (It will be very stiff so mash it in, and add more whites until it’s soft enough to fold in the rest.)
Fold in the rest of the egg whites.
Pour into prepared pan.
Bake for 35 minutes until tester comes out clean.
Cool in pan, then un-mold and turn onto a serving platter.
Sprinkle with powdered sugar and slivered almonds.
Makes 12 slices, serving size is one slice
*You can purchase almond flour or almond meal; the latter is ground with skin. You may also grind your own in a food processor or blender, using about 1½ to 2 cups of almonds.
Serving size: 1 slice Calories: 140
Recipe by gfe--gluten free easily at http://glutenfreeeasily.com/almond-recipes-almond-board/