Preheat the oven to 180C/160 Fan. Line your Bundt tin and leave it to one side.
In a large bowl, cream together the sugar and butter until light and fluffy.
Add in the flour, eggs and baking powder and whisk until all combined.
Add in the blackberries and the Prosecco and mix again until completely combined.
Spoon the mixture into the Bundt tin.
Bake in the oven for 55 minutes to 1 hour. You will know the cake is ready when it is golden brown and springy to touch.
Leave to cool completely.