Pre-heat oven to 180 degrees. Grease a tube pan with butter. Cut 1 orange into half and cut each half into slices. Place the slices flat on the pan with the skin/round side towards the tube. Set aside.
Put half the sugar into a small saucepan. Zest and Juice the second orange and add it to the sugar. Bring to boil on medium heat for 3 minutes to form a syrup.
Pour in the two shots of Italian Apéritif, reduce heat to low and simmer for 5 minutes. Set aside to cool.
Separate the eggs into two bowls and in one bowl whisk the egg whites with the remaining sugar until stiff peaks. Set Aside.
Mix the flour, baking soda and powder in one boil and in another bowl whisk egg yolks, milk and sunflower oil. Combine both dry and wet mixture into a cake batter.
Gently fold in the egg white mixture into the cake batter until combined. (It's ok if there are white stripes of egg white, try not to over mix, so you don't lose air)
Pour the already cooled syrup into the pan with the sliced oranges. Gently scoop the cake batter into the pan, be careful not to shake or move the oranges and syrup around.
Bake in a pre-heated oven at 180 degrees for 40 minutes or until a skewer inserted comes out clean. Remove from oven and allow to rest for 5 - 10 minutes before you turn and gently let the cake out unto a flat surface. Let cool before serving or serve warm.