Combine the flour, cornstarch, baking powder, baking soda, salt and poppy seeds in a bowl and set aside.

Cream sugar and oil on high speed until light and fluffy. Add eggs, zest, juice, and vanilla and mix until thoroughly combined.

Stir in flour mixture and mix well.

Lightly oil or wet your hands and then divide dough into four portions. Gently handle each portion as you form a uniform log that is about 12 inches long, 2 inches wide and 1 inch high. Place 2 logs on each parchment paper lined cookie sheet.

Sprinkle the tops of the loaves with the cinnamon and sugar mixture.

Bake at 350F for 20 minutes, or until edges are golden brown.

Remove the loaves from the oven. Let cool for 5 minutes. Slice horizontally into 1/2 inch cookies. Place slices cut side up on the sheets and bake for 5 minutes. Turn cookies over and bake for another 5 minutes. Cool and then store in air tight container for 2 weeks or freeze.