Summer Berry Slice

OK, this isn't really a slice, it's more a tray bake, but it's delicious whatever you call it. I've made it with blueberries, raspberries, mixed berries and strawberries and have never had to worry about it going stale. There's no chance of leftovers when you serve this cake for afternoon tea or dessert (it goes very well with whipped cream and/or ice cream).

Ingredients:
100g butter
200g caster sugar
1 tbsp caster sugar, extra (try raw sugar or coffee crystals for a change)
Finely grated zest of  one lemon
1 egg
1 tsp vanilla extract
300g self raising flour
½ tsp baking powder
300g fresh soft berries (or 300g frozen berries, thawed and drained overnight)
140ml buttermilk (MOO it!)

Method:
Preheat oven to 180 degrees Celsius. Line a 20cm square tin with baking paper.  Cream butter, lemon zest and sugar until light and fluffy.  Add the egg and vanilla and beat well. Gently toss the fruit in two tablespoons of the flour (this stops the fruit sinking to the bottom of the cake).  Mix the remaining flour and baking powder together; add to the batter a little at a time, alternating with the buttermilk. Gently fold in the berries. Spoon the cake mix into the prepared cake tin and sprinkle the extra sugar over the top. Bake for 25 minutes or until a skewer inserted in the middle comes out clean. Allow to cool in the pan for 10 minutes before lifting the cake out onto a cooling rack.