Preheat oven to 180 degrees Celsius (165 degrees if fan-forced). Spray a bundt pan (9 inch; 22cm) with vegetable oil and set aside.
In a mixer, whisk the egg whites and gradually add in 1 third of the sugar (25 grams). Whisk until stiff peaks form and set aside.
In a separate bowl, whisk the egg yolks gradually adding in the second 25 grams of sugar until pale and fluffy.
Fold in the egg whites with the egg yolks.
Add in the remaining sugar, flour, grape seed oil and mix thoroughly, taking care to not overly beat the mixture and lose the air.
Add in the blueberry yoghurt and mix through gently.
Gently pour the mixture into the prepared bundt pan and bake for 45-55 minutes (or until a toothpick/skewer comes out clean).
Let the cake cool in the pan for 5 minutes before turning over and releasing to a cake stand.