Preheat oven to 350 F. Grease and flour a 10-inch springform pan.
Mix together butter and olive oil.
In a separate bowl, beat together eggs, sugar, and orange zest for about 3 minutes.
Mix dries together and add to the egg mixture alternately with the butter/olive oil mixture.
Pour batter into prepared pan and bake for 25-30 minutes, or until a cake tester comes out clean.
Spread lemon curd over the entire top of the cake and garnish with candied orange slices (both recipes below).