Named after a town in the Vaucluse and the sweet, fortified wine produced there.

Preheat oven to 400°F. Brush 10-inch-diameter spring form pan with olive oil. Line bottom of pan with parchment; brush parchment with olive oil.

Sift flour and next 3 ingredients into bowl. Whisk ¾ cup sugar, 6 tablespoons butter and 3 tablespoons oil in large bowl until smooth. Whisk in eggs, both peels and vanilla. Add flour mixture alternately with the wine in 3 additions each, whisking just until smooth after each addition. Transfer batter to prepared pan; smooth top. Sprinkle grapes over batter.

Bake cake until top is set, about 20 minutes. Dot top of cake with 2 tablespoons butter; sprinkle 2 tablespoons sugar over. Bake until golden and tester inserted into center comes out clean, about 20 minutes longer. Cool in pan on rack 20 minutes. Release pan sides. Serve slightly warm or at room temperature.