1. Preheat oven to 325* grease several baking sheets or use nonstick spray.
2. In a medium bowl, thoroughly stir together the flour, coriander, baking soda and salt; set aside. In a large bowl, with electric mixer on low speed, beat together the butter, oil and 1 cup of powdered sugar until blended. Increase the speed to medium and beat until very well blended. Add the egg, lemon juice, lemon extract, and orange and tangergine zests and beat until lightened and smooth.
3. Beat or stir in flour mixture until evenly incorporated.Let dough stand for 5 minutes, or until firmed up slightly. Shape portions of dough into generous 1 balls with lightly greased hands.
4. Place on baking sheets, spacing about 1 apart. Using you hand, press down the balls just until their tops are flat. Bake the cookies, one sheet at a time, in the upper third of the oven for 14-18 minutes, or until the bottoms are nicely browned; lift cookie up to check. Reverse sheet from from to back halfway through baking to ensure even browning.
5. Transfer the sheet to wire rack and let stand until cookies firm up slightly, 1-2 minutes.Using a spatula, transfer cookies to wire rack to cool to barely warm.In a large shallow bowl, place the remaining 1/2 cup powdered sugar.
6. Place the cookies in the bowl, 3 or 4 at a time, and turn them to coat all sides well. Store the cookies in an airtight container, sifting additional powdered sugar over each layer.
7. Store in a cool place, but not refrigerated. for up to 2 weeks or freeze for up to 1 month.If freezing, powdered sugar coating should not be added till after the cookies are completely thawed.