Preheat the oven to 180°C/350F/gas mark 4. Grease an 8inch/20cm cake tin with butter then dust with flour making sure all the edges are covered, remove any excess flour.
Soak the sultanas in warm water for 10-15 minutes.
Put the olive oil and sugar in a bowl and using a stand mixer or electric whisk mix together for 2 minutes until thoroughly combined. Add the eggs one at a time and continue to whisk until the mixture increases in volume and becomes thick but still runny (around 1-2 minutes).
Add the flour, cinnamon, baking powder, bicarbonate of soda to a bowl. Gradually sift the dry ingredients into the wet whilst folding the mixture with a metal spoon.
Once combined (it will be a thick, stiff batter) add the sultanas, apple and lemon zest to the batter and mix with a metal spoon until thoroughly combined.
Spoon the mixture into the cake tin and level the top with the back of a spoon. Bake in the oven for 45 minutes or until an inserted skewer comes out clean.
Cool on a wire rack, serve.