Preheat oven to 325˚F. Spray a 9 x 5 baking pan with non-stick baking spray and line with parchment paper. Leave a 1 to 2-inch overhang beyond the edges of the pan for easy removal of the cake once baked.
In a medium bowl, whisk together the flour, cake flour, baking powder and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium high speed for 3 to 4 minutes. It will be light and creamy.
With the mixer on medium low speed, slowly add the sugar until fully incorporated. Mix for 30 seconds. Add the eggs, followed by the egg yolks, one at time. Mix on low speed thoroughly between additions and scrape down the sides of the bowl as needed.
Add the vanilla and mix to combine. Add the dry ingredients to the butter and egg mixture, alternating with the orange juice. Begin and end with the flour mixture. Beat on low speed only until just combined and a few streaks of flour remain.
Add the orange zest and gently stir into the batter with a large spatula. Do not over mix.
Transfer the batter to the prepared baking pan and bake for 55 to 60 minutes or until the top is golden brown and a toothpick inserted in the center of the cake comes out clean or with a few crumbs remaining. If the top is browning too quickly at the end of the baking cycle, loosely tent the top of the cake with a piece of aluminum foil.
Remove from the oven and cool completely before adding the glaze.
Mix all ingredients together with a whisk until smooth and pourable. If too thin, add more confectioners’ sugar. If too thick add more orange juice or milk. Drizzle over top of the cooled cake.
Store tightly covered at room temperature for up to 4 days. May be frozen.