Preheat oven to 400 degrees
Grease and flour a large angel food cake or chiffon pan
Sift the flour, baking powder, baking soda, and salt into bowl and set aside
Place the sugar in the bowl of an electric mixer with paddle attachment
Add butter, olive oil, lemon zest, orange zest, and vanilla and beat for 2 minutes on medium high until smooth and fluffy
Add eggs one at a time, beating well after each addition
Turn speed to low and add flour and Somerset Ridge Aphrodite until fully mixed
Pour into prepared cake pan
Scatter grapes evenly on top
Bake for 20 minutes
While baking -place softened butter and sugar in bowl and beat until forms a thick paste
Remove cake at 20 minutes quickly and gently
Dot sugar paste evenly over top of cake
Scatter grapes evenly over top
Lower oven temperature to 350 degrees
Return to oven and bake for 40 minutes or until inserted toothpick comes out clean
Let sit for 30 minutes before removing from pan