Preheat oven to 350 F. Line several baking sheets with parchment paper. In a small cup stir egg, egg yolk and vanilla together with fork and set aside. Place the flour, sugar, cinnamon, baking powder, cocoa powder, salt and lemon zest in food processor and blend for about 5 seconds. Place the butter all around the top of the flour mixture and process until coarse (20-30 seconds). Now add the egg mixture through the feed tube with the machine running and process for 3 seconds. Scrape bowl and process for 3 more seconds. Remove dough and shape into 2 disks. Between plastic wrap, roll each piece of dough out to 1/8" thickness. Remove the top piece of plastic wrap and using a Linzer Cookie Cutter cut out appr. 20 bottom cookies (fluted bottom) and 20 top cookies (cookie with center out, injector). Place all the rounds on the baking sheet about 3/4" apart on the prepared baking sheets. Gather up the dough scraps and reroll the dough to make as many more cookies as possible, again using half for tops and half for bottoms. Bake the cookies until they are firm, for about 15 minutes. Remove them and let them cool on the sheets. When they are completely cool, turn the cookies with no holes upside down and spread with your favorite filling, then place another 1/2 tsp. of filling in the center and sprinkle with confectioner's sugar and top with the top cookie (cookie with design hole in center).