Preheat oven to 350°F, lightly grease a two piece tube pan with butter and dust lightly with flour. Shake out excess flour.
Separate the eggs, add the yolks to a bowl along with sugar and oil and whisk vigorously for several minutes until the mixture is pale yellow, thick and forms ribbons when you lift the whisk out of the bowl.
Use a rubber spatula to gently fold the egg whites into the batter.
Pour the batter into the prepared cake pan and bake for 50 minutes in the center of the oven until a toothpick inserted in the cake comes out clean.