Butter and flour for preparing the cake pan
2 large eggs, at room temperature
2/3 cup (135 g) sugar
4 tablespoons (2 ounces; 60 g) unsalted butter, melted
1/4 cup (6 cl) extra-virgin olive oil
1/3 cup (8 cl) whole milk
1/2 teaspoon pure vanilla extract
1 1/2 cups (200 g) unbleached all-purpose flour
3/4 teaspoon baking powder
A pinch of sea salt
Zest of 1 lemon, grated
Zest of 1 orange, grated
10 ounces (300 g) small, fresh purple grapes (see headnote suggestions for varieties)
Equipment: One 9-inch (23-cm) springform pan
1. Preheat the oven to 350 degrees F (175 degrees C; gas mark 4/5).
2. Generously butter and flour the spring form pan, tapping out any excess flour. Set aside.
3. In the bowl of an electric mixer fitted with a whisk, beat the eggs and sugar until thick and lemon-colored, about 3 minutes. Add the butter, oil, milk and vanilla extract, and mix until blended.
4. Sift the flour, baking powder and salt into a large bowl. Add the lemon zest and orange zest, and toss to coat the zest with flour. Spoon the mixture into the bowl of batter and stir with a wooden spoon until thoroughly blended. Scrape down the sides of the bowl and mix once more. Set aside for 10 minutes to allow the flour to absorb the liquids.
5. Stir in about 3/4 of the grapes into the batter. Spoon the batter into the prepared cake pan and smooth out the top with a spatula
6. Place the pan in the center of the oven. Bake for 15 minutes, than sprinkle the top of the cake with the remaining grapes. Bake until the top is a deep golden brown and the cake feels quite firm when pressed with a fingertip, about 40 minutes more, for a total baking time of 55 minutes. Remove to a rack to cool. After 10 minutes, run a knife along the sides of the pan. Release and remove the side of the springform pan, leaving the cake on the pan base. Serve at room temperature, cut into thin wedges.
EIGHT TO TWELVE SERVINGS
WINE SUGGESTION: Grape cake is an ideal match for vin santo, the rich, smooth, aromatic sweet wine prepared in small quantities on many Italian estates