Preheat the oven to 350°F and butter an 8-inch square baking dish (or one with an equivalent volume).
In a small bowl rub the orange zest and sugar together and set aside. This will bring out the oils in the zest and perfume your cake. Whisk together all of the dry ingredients and set aside.
Cream together the butter and sugar on medium speed, about 3 minutes until light. Add the eggs one at a time, beating for about 1 minute after each. Add the vanilla and mix in well.
Reduce the mixer speed and add the flour mixture and the buttermilk alternately, the flour in 3 parts and the buttermilk in 2. You will end up with a think batter. With a rubber spatula spread it evenly in the pan. Add the fruit decoratively over the batter.
Bake for about 50-60 minutes, or until it is golden brown and a skewer comes out clean. Serve with vanilla ice cream!
