Preheat oven to 325. Mix together flour, baking powder, and salt; set aside. Cream butter and sugar until light and fluffy. Beat in eggs one at a time. Add vanilla and orange extract. Blend in 1/3 of the flour mixture then half of the orange juice/milk mixture. Blend in half of the remaining flour mixture, then the rest of the orange juice/milk mixture, and then finally the remaining flour mixture. Mix at medium speed until ingredients are thoroughly blended (about 1 or 2 minutes). Tint cake batter orange. Pour batter into two 8" round prepared cake pans. Bake for 35 to 40 minutes, or until a toothpick comes out clean when inserted in the center of the cake layer. Cool 15 minutes before turning out on to cooling racks.
To make the filling:
Combine sugar and cornstarch in a small sauce pan. Add remaining filling ingredients and mix well. Cook over medium heat stirring continuously until mixture comes to a boil. Boil for 1 minute. Pour filling into a container and chill in the refrigerator.
To make the icing:
Whip cream to soft peaks. Gradually whip in sugar. Mix in vanilla. Mix in orange juice concentrate to taste. Add orange food coloring.
To assemble the cake:
Split the two cake layers in half so you have four layers. Lay the first layer on a plate. Pipe a small border of the whipped cream on the layer at the edge. Fill the center of the cake layer with 1/3 of the orange filling. Repeat with the remaining layers. Starting at the bottom you should have cake, filling, cake, filling, cake, filling, cake. Ice the outside of the cake with the remaining orange flavor whipped cream. Chill cake in the refrigerator for several hours before serving.
I usually color the cake batter a medium orange, the filling a dark orange, and the whipped cream a pale orange.