Preheat the oven to 400 and butter a 9-inch round cake pan (and 8×8 square should work too).  Whisk together the flour, baking powder, baking soda and salt and set aside.

Using your electric mixer, beat together the butter and sugar for a couple of minutes until fluffy, then add in the vanilla and zest and beat, then the egg and beat again.  Turn the mixer to low and carefully add the flour mix in 3 batches, alternating with the buttermilk, beginning and ending with the flour.  Scrape down the sides of the bowl as needed and mix until all traces of flour are gone.

Scrape the batter into your prepared pan, level the top, scatter the raspberries as evenly as possible overtop, then sprinkle on a bit of sugar for some crunch.

Bake for 20 to 25 minutes until the center is set and the cake is a lovely golden brown.  Leave the cake in the pan for about 10 minutes before inverting it out onto a rack or platter to cool completely.