Grease a 23cm-deep, loose-bottomed cake tin and cut out a circle of baking parchment to fit into the bottom. Cut a thick strip of parchment to fit around the side of the tin. Heat oven to 190C/fan 170C/gas 5. Put the sugar and butter into a large mixing bowl. Using an electric whisk (or wooden spoon if you’ve got more time and energy), beat them together until creamy and soft. Crack in the eggs, one by one, giving a good beat after each addition. Stir in the vanilla extract, then the flour and baking powder, then stir through the milk to loosen the mixture. Carefully stir in half the raspberries, making sure you don’t mix too vigorously or they will fall apart.