This delicous cake gets its unique flavors from olive oil, muscat and fresh grapes.
Preheat oven to 400F and grease an angel food cake or 2 x 8 " round pans.
Sift the flour, baking powder, baking soda, and salt and set aside.
Place the butter, sugar, olive oil, and zests in a bowl of a standing mixer fitted with the paddle attachment and beat on medium-high until you have a light and fluffy mix.
Add the eggs one at a time, waiting for each to fully incorporate before adding the next. Scrapes the sides and bottom of the bowl.
Add the flour in three additions alternating with the wine.
Pour batter into the pan(s) and dot with the grapes on top.
Bake in the middle rack for 20 minutes (15 for 8" pans)
While the cake is baking, mix the butter and sugar using a spoon until it is smooth.
At the end of the 20 minutes, remove the cake from the oven and dot the topping mix, followed by the grapes.
Reduce oven temperature to 350F and bake for 35-40 minutes longer or until a wooden skewer comes out clean from the center of the cake.