An easy delicious cake to make in late summer early fall when champagne grapes appear at the market
Preheat oven to 350F
Butter and flour a 9 inch springform pan (I used "Spectrum" canola oil spray with flour)
Combine the eggs and sugar in a large bowl. Using an electric mixer, whisk for about 3 minutes. Add the butter, oil, milk, and vanilla mixing completely.
In a medium bowl, combine flour, baking powder, and salt. By hand whisk together. Add lemon and orange zest, whisking to combine and coat zest with the flour.
Slowly add the flour mixture to the batter. Mix at low speed until combined. Let rest for 10 minutes.
Add 3/4 of the grapes to the batter, gently mix. Pour the batter into the prepared springform pan.
Bake for 15 minutes. Remove cake from the oven and sprinkle the remaining grapes over the top of the cake. Return the cake to the oven, continue baking for about 40 minutes or until the cake is firm and golden with the edges pulling away from the side of the pan.
Cool for 10 minutes. Remove the side of the springform pan and let cake cool to room temperature. Sprinkle with the powdered sugar before serving.