Combine oil and sugar with a wooden spoon. Gradually stir in eggs and vanilla.
Sift flour, baking powder and salt 3 times and stir carefully into mixture. Add apple and stir to mix. Pour batter into a previously buttered and floured tube cake pan.
Bake in the middle of a preheated oven to 350ºF (180ºC) for 50 – 55 minutes or until cooked.
Remove from the oven and cool on rack. Invert onto a serving platter.