Preheat oven to 150°C fan-forced.
Weigh the sugar in a medium bowl. Take out 2 tablespoons to add to the egg whites later. Add the flour, baking powder and salt to the bowl and set aside.
Place the egg whites and cream of tartar into the bowl of a stand mixer. Using the whisk attachment, whip on medium-high speed (speed 6) until the egg whites are stiff and white. Start adding the reserved sugar to the egg whites gradually (about a teaspoon every 30 seconds) and beat until you have a white, smooth, glossy mixture. Then beat on low (speed 1) for 1 minute to remove any air bubbles.
Put the oil, egg yolks and juice and zest in a wide bowl and whisk to combine. Sift the dry ingredients over the yolk whisk together to form a loose batter. Gently fold in one-third of the egg white mixture with a silicone spatula. Then add in the remaining egg white mixture and gently combine until no white streaks remain.
Pour the mixture into the cake tin, wiping away any batter smears around the sides or centre of the tin. Bake for 55-60 minutes or until golden and the cake around the centre tube looks dry. Wearing oven mitts, remove from the oven and immediately invert the centre tube onto a bottle. Let it hang for 2-3 hours or until the tin is completely cool.
To release the cooled cake, run a thin knife around the edge of the tin, ensuring you get right to the bottom. Turn the chiffon cake out onto a serving plate.
To make the yuzu yoghurt glaze, sift the icing sugar into a bowl, add the yoghurt, most of the zest and juice. Stir well until combined. Add a little extra icing sugar if too wet, or a small amount of water or yoghurt if too thick.
Spoon the glaze around the outer edge of the cake first, then over the top. Sprinkle over remaining zest. Leave to set for 15 minutes before serving.
