Preheat your oven to 350-degrees. Using shortening, grease only the bottom of a tube pan, avoiding the sides of the pan.
In a medium mixing bowl, whisk together the cake flour, baking powder, kosher salt and one cup of the sugar.
In a large mixing bowl, combine the flour mixture with the vegetable oil, orange zest and juice, water, egg yolks, vanilla and the orange extract.
Using medium speed, beat until the batter is smooth and well blended, about 2 minutes.
Place the egg whites and the cream of tartar in a separate bowl. Using a clean whisk attachment, beat on medium-high speed until soft peaks are formed, about 30 to 60 seconds.
Add the remaining sugar and continue beating on medium-high speed until the peaks are stiff and glossy, about 1 minute.
Using a large spatula, gently fold the meringue into the batter about 1/3 of it at a time, taking care not to deflate the meringue.
Pour the batter into the prepared tube pan. Run the spatula through the batter to break up any air bubbles.
Bake for 40 to 45 minutes or until a toothpick inserted into the center comes out clean and the cake springs back when gently pressed with your finger.
Invert the cake over the neck of a bottle (a wine bottle works great for this) and allow it to cool completely before removing the cake from the pan, about 2 hours.
To remove the cake, flip it back over and take a long sharp knife to gently work the cake loose from the sides and then the bottom of the pan.
Sift powdered sugar over the top and garnish with orange slices. Serve with sweetened whipped cream.