Preheat oven to 325 degrees. Spray a 10" tube pan with cooking spray.

Sift flour and measure out 2 ¼ cups into a large bowl. Add the baking powder, sugar and salt. Whisk to combine. Make a well in the center.

Whisk the oil, egg yolks, mandarin juice in a measuring cup. Stir liquid into the well of the dry ingredients and mix well.

In a separate bowl, beat the egg whites with the cream of tartar until it forms stiff peaks but are not dry.

Add ⅓ of egg white mixture into the orange mixture and fold in gently. Add the second third of egg whites and fold in. Fold last of the egg whites in gently til evenly combined.

Pour the batter into the cake pan. Bake for 55-65 minutes until until a toothpick in the center comes out clean. Start checking for doneness after 55 minutes.

When cake is done invert the cake pan over a small jar or long necked bottle to cool. When cool run a knife along the inner and outer edges of the tube pan as well as under the bottom rim of the pan.

Place a cake plate on top of tube pan, invert and gently remove the tube pan. Split the cake in half and gently tranfer the top portion to a side plate. Use an offset spatula to help support the top layer so it doesn't crack.

Beat all filling ingredients in a small bowl until evenly mixed and smooth.

Beat all Frosting ingredients in a separate bowl until well mixed and smooth.

Spread filling over bottom half of the cake. Gently position the top layer on the filling.

Gently spread the Frosting over the top layer and the sides of the cake. Decorate with mandarin pieces.

Refrigerate cake for 4 hours to allow frosting to set. Remove from fridge about 20 minutes before serving.