Preheat oven to 170 C / Gas 3. Grease a 25cm tube cake tin with 2 tablespoons butter. Sprinkle tin with 4 tablespoons sugar. Mix together 350g flour, baking powder and salt. Set aside.
In a large bowl, cream together 220g butter and 400g sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla. Gradually beat in the flour mixture. Dredge blueberries with remaining flour, then fold into cake mixture. Pour mixture into prepared tin.
Bake in the preheated oven for 70 to 80 minutes, or until a skewer inserted into the centre of the cake comes out clean. Let cool in tin for 10 minutes, then turn out onto a wire rack and cool completely.