Lemon Biscotti with Sour Lemon Drizzle

This is a real treat for lemon lovers. If you're cooking enough to freeze, store them in the freezer without the frosting, then cook and add before serving.
Preheat the oven to 350 degrees.Lightly pour the flour into dry measuring cups; smooth with a knife. Combine the flour, sugar, and baking powder in a large bowl. Combine the zest, 1 tablespoon of lemon juice, extract, butter and eggs and add to the flour mixture, stirring until smooth (the dough will turn out dry and crumbly). Place the dough on a lightly floured surface; knead lightly 7-8 times. Divide the dough in half. Form each serving into an 8-inch long roll. Place the rolls 6 inches apart on a baking sheet greased with cooking spray; flatten each roll to a thickness of 1 inch.Bake at 350 ° C for 30 minutes. Remove the rolls from the baking tray; cool for 10 minutes on a wire rack. Cut each roll diagonally into 15 (1/2-inch) slices. Place the slices side down on a baking sheet. Reduce the oven temperature to 325 degrees; bake for 10 minutes. Turn the cookies over; bake for another 10 minutes (the cookies will be slightly soft in the center, but will harden as they cool). Remove from the baking tray and allow to cool completely on a wire rack.Combine 1 tablespoon of lemon juice and powdered sugar and sprinkle over the biscotti.