Preheat oven to 350 degrees. Spray a 9-inch springform pan with non-stick spray. Line the bottom of the pan with a circle of parchment paper, then spray the paper with non-stick spray also.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar on high speed for about 90 seconds, until light and fluffy. Then add the eggs and continue beating. Incorporate the vanilla and sour cream until smooth.
In a medium bowl, stir together the flour, baking powder, baking soda, and salt. With the mixer on low, add the flour mixture to the wet ingredients and beat gently until it just comes together and becomes a thick batter, being careful not to over mix. Scrape the side of the bowl as needed. Carefully spread the batter evenly into the prepared springform pan with an offset spatula. Lay the nectarine slices over the top of the cake. Sprinkle the top of the cake with blueberries and press all of the fruit lightly into the batter lightly. Sprinkle all of the fruit with 1 tablespoon sugar.
Bake the cake for 50-60 minutes or until cooked through in the center. Allow the cake to cool for at least 30 minutes before releasing the cake from the springform pan and removing the parchment paper. Dust the cake with powdered sugar before slicing and serve with freshly whipped cream.