Preheat the oven to 340ºF. You'll need a 7-inch chiffon pan—but don't grease it. Line the bottom with parchment paper, but leave the sides bare; the cake needs to cling to the sides. You'll also need a large baking pan you can fill with water bath, and then place the cake pan inside.

Add the egg whites to a medium sized bowl. Place it in the fridge until you are ready for it.

Add the egg yolks to a medium sized bowl. Beat until lemon colored. Add most of the sugar as you continue to beat, reserving about 2 or 3 tablespoons.

Beat in the orange juice, oil, and salt until the mixture is smooth.

In a separate bowl, measure all the flour, baking powder, ground cardamom, and orange zest. Mix together until well blended.

Blend the flour mixture with the egg yolk mixture, folding the batter over until well blended.

When it's smooth, take the bowl from the fridge, and beat the egg whites until they are stiff, adding the last of the sugar as they begin to stiffen.

Fold about a third of the beaten egg white into the batter, until the batter is only just blended.

Repeat with the remaining two thirds of the egg whites. Avoid over mixing - success depends on keeping the batter light.

Place the pan of water (at least 1 1/2") into a middle rack of the oven.

Transfer the cake batter into the chiffon (or similar cake) pan. Place it gently in the water bath.

Bake for 30 to 40 minutes. You may have to turn the pan once or twice to avoid over browning on one side.

Reduce the heat to 250°F. Bake for another 15 to 20 minutes. The top should spring back when you touch it gently.

Remove from the pan, and allow to cool.

Garnish with icing sugar and/ or orange zest, as desired.