To make the cake, preheat the oven to 325°F (160°C).
Zest one orange.
Sift together cake flour and half of the sugar (¾ cup).
In a large mixing bowl with whisk attachment, beat the egg whites until foamy on a low speed.
Add cream of tartar and salt and continue to beat, gradually increasing the speed to high.
When the egg whites get whiter, add remaining ¾ cup of sugar one tablespoon at a time.
Add orange blossom water and orange zest and continue to beat on high speed until hard peaks form.
Transfer the whipped egg whites into a large bowl.
Add flour/sugar mixture and carefully mix everything together. Be careful not to deflate the batter too much.
Now transfer the batter to ungreased angel food cake pan. Even out the surface. Run a butter knife through the batter to remove any air bubbles.
Bake for about 40-45 minutes. It’s ready if the inserted wooden stick comes out clean.
Cool the cake completely in the pan upside down for 90-120 minutes. This will make sure the cake stays soft and fluffy while cooling.
Make orange curd, while the cake is baking.
In a small saucepan, mix sugar, cornstarch and salt and slowly stir in orange juice.
Heat the mixture over medium high heat. Cook and stir until mixture is thick and bubbly. Turn the heat down and cook one more minute.
In a small bowl, beat egg yolks. To temper the egg yolks, stir in ½ cup of hot sugar mixture, while whisking constantly to prevent scrambling the egg yolks.
Transfer the tempered egg yolk mixture back to remaining hot sugar mixture.
Cook for couple more minutes, stirring constantly.
Add butter and orange zest.
Transfer the curd into a clean bowl and cover with plastic wrap, making sure the plastic touches the curd to prevent any skin to form.
To make the glaze, in a medium bowl combine powdered sugar and orange juice. Mix until nice and smooth. Stir in orange blossom water.
Pour the glaze all over the cake and serve with orange curd on the side.