For the cake batter:
1 1/2 cups all-purpose flour
1 tsp. baking powder
1/2 tsp. baking soda
1/4 tsp. salt
1/2 cup butter softened
3/4 cup brown sugar packed
1 tsp. vanilla
2/3 cup sour cream
1 peach peeled, pitted and cut into large chunks
1/2 cup fresh blueberries or a bit more, if you like
For the top of the cake:
2 peaches unpeeled and cut into thin slices
1/2 cup fresh blueberries
Turbinado white or brown sugar, for sprinkling over-top
Preheat oven to 350 F.
In a medium bowl, whisk together the flour, baking powder, baking soda, salt and nutmeg. Set aside.
In a large bowl with an electric mixer or in the bowl of a stand mixer fitted with the paddle attachment, beat the butter with the brown sugar until light and creamy, about 2 minutes. Add eggs one at a time, beating well after each addition. Add vanilla and sour cream and mix in. Scrape down side of bowl as needed. Add flour mixture and mix until smooth and well combined.
Fold chunks of peach and 1/2 cup blueberries in to the batter, then spread the batter into a greased skillet (10-inch top diameter works well) or a 9-inch cake or springform pan. Arrange peach slices in a circular pattern on top of the batter, around the outside of the cake. Fill the centre with a mound of blueberries.
Bake in pre-heated 350 F. oven for 45-50 minutes, or until deep golden and a tester inserted near the centre comes out clean.