In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar until light and fluffy (3-4 minutes).
Beat in the egg, mixing until fully incorporated.
In a large bowl, whisk together the flour, baking powder, salt, and orange peel.
Add the dry ingredients and buttermilk to the mixture in the stand mixer, alternating 3 times, starting with dry and ending with the buttermilk.
Remove bowl from mixer and fold in the blueberries.
Spread into the prepared dish and set aside.