Preheat your oven to 350°F (175°C). Grease and flour a 10-inch Bundt pan or a 9x13-inch baking pan.
In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt.
Add the eggs, milk, and vegetable oil to the dry ingredients. Beat with a mixer on low speed until the batter is smooth and well combined.
Stir in the orange zest, orange juice, lemon zest, lemon juice, and the 1/3 cup (80ml) of Prosecco until fully incorporated.
Pour the batter into the prepared pan. Bake for 40 to 50 minutes, or until a toothpick inserted into the center comes out clean. For food safety, ensure the internal temperature reaches 160°F (71°C) to fully cook the eggs.
Let the cake cool in the pan for 10 minutes, then turn it out onto a wire rack to cool further.
While the cake cools, whisk the powdered sugar, 2 tablespoons (30ml) of Prosecco, and 2 tablespoons (30ml) of lemon juice in a small bowl until the sugar dissolves.
Use a pastry brush to coat the warm cake with the Prosecco glaze. Let the glaze set.
In a separate bowl, toss the mixed berries with the remaining 1/4 cup (60ml) of Prosecco. Let them sit for 15 minutes before serving alongside slices of the cake.