Preheat oven to 350°F. Line 8-inch round baking pan (or similar size) with parchment paper.
In a large bowl, beat butter and sugars together until light and fluffy, about 4 - 6 minutes with electric mixer. Add eggs one at a time, beating well after each until combined. Add vanilla and mix until well blended.
In a separate bowl, whisk together flour, cinnamon, baking powder, baking soda and salt. Add to the creamed mixture, beating until just combined. Scrape the batter into prepared pan (batter will be thick) and spread out into an even layer.
Arrange nectarine slices on top of batter, then randomly sprinkle over the blueberries. Bake in preheated oven for 25 - 35 minutes, until cake springs back when pressed in the center. Allow to cool in the pan for 10 - 15 minutes. Lift out of pan using parchment as handles and cool another 5 minutes. Dust with powdered sugar and serve.
Chef Tips
If using salted butter, reduced added salt in recipe to 1/4 teaspoon.Granulated (white) sugar can be substituted for the brown sugar.