Preheat your oven to 350°F and spray a 10-inch skillet with nonstick spray with flour.
Beat the butter until creamy. Add the sugar and beat until fluffy. Add the eggs and almond extract and beat to combine. Gradually add in 1/3 of the cake flour, baking powder, and salt with 1/2 of the buttermilk. Mix and add 1/3 of the flour and remaining buttermilk, mix and then add the remaining flour until just combined. Stir in the almonds by hand.
Pour the melted butter into the skillet and stir in the brown sugar. Add the blackberries and pour the batter over the blackberries.
Bake for 40 to 45 minutes and test doneness with a toothpick. Let cool in the skillet for 30 minutes, then invert it onto a plate and let cool completely. Slice and serve.