Step 2

Cut the hard bits from the top and bottom of the orange. Slice and remove all seeds. Puree the whole orange including the peel in a food processor. Add one third of the sugar and the olive oil and blitz until well combined.

Step 3

Sift together the flour and baking powder.

Step 4

Beat the eggs with the remaining sugar using an electric hand mixer for at least 5 minutes until very light and fluffy.

Step 5

Fold in half the flour mixture, then the orange mixture and vanilla extract, then fold in the remaining flour. Mix well but briefly.

Step 6

Pour into the prepared pan and smooth the surface. Bake for 20 minutes at 375°F.

Step 7

Reduce temperature to 325°F / Gas 2 and bake for a further 30 minutes until golden brown and a skewer comes out clean.

Step 8

Cool on a wire rack before serving.