Preheat your oven to 325°F (165°C).
Sift together the cake flour, 1/2 cup sugar, and baking powder.
Mix in the egg yolks, orange soda, and vegetable oil until smooth.
In a separate bowl, beat the egg whites and cream of tartar until foamy.
Gradually add the remaining 1/2 cup of sugar, beating until stiff peaks form.
Gently fold the meringue into the cake batter until well combined.
Pour the batter into an ungreased chiffon cake mold and bake for 1 hour and 1 minute.
Cool upside down before removing from the mold and dusting with powdered sugar if desired.
Serve and enjoy!