Preheat oven to 400 degrees. Lightly butter 4 oven proof dessert dishes. Sprinkle sides and bottom with 4 Teaspoons castor sugar. Place 1/2 cup blueberries into each dessert dish. Set aside.
In the bowl of an electric stand mixer beat the cream cheese,the remaining 1/2 cup caster sugar, flour, vanilla, and 1 egg until well blended. Add the remaining 2 eggs and mix till well blended. Gradually beat in the milk. Pour the batter into the dessert cups to about an inch from the top of the dish. Top each cup with grated lemon zest. Place dessert dishes on a baking sheet and place in the oven. Bake for 20 minutes or until golden brown on top. Test with a toothpick, place toothpick in the center of the dessert, if it comes out clean it's done. Cool slightly, sprinkle with powdered sugar and serve warm.