Preheat oven to 325 degrees. Place 4 tablespoons butter in a 9-inch round cake pan (2 inches deep) and melt in oven. Remove pan from oven and sprinkle brown sugar evenly over butter.
With two double-thick layers of paper towels, press as much liquid as possible out of nectarines. Arrange fruit in an even layer in pan.
In a medium bowl, stir together flour, baking powder, baking soda, and salt. In a large bowl, using an electric mixer, beat 6 tablespoons butter on high until light and fluffy. Add granulated sugar and beat until well combined. Beat in eggs, one at a time, scraping down bowl as needed. Beat in vanilla. With mixer on low, add flour mixture in three additions, alternating with two additions yogurt, and beat to combine.
With a spatula, spread batter over nectarines. Bake until cake is dark golden brown and a toothpick inserted in center comes out clean, 1 hour 10 minutes. Let cake cool in pan on a wire rack, 15 minutes. Run a knife around edge of pan and invert cake onto a serving plate. Serve warm or at room temperature.
Pressing excess liquid from the thawed fruit makes all the difference in the texture of this cake, so don't rush that step.
Does not take 1 hour 10 minutes to bake. Check after 45 minutes. Very tasty!
I disagree with both of the previous commenters. I definitely needed the full bake time, and the cake came out perfectly... sort of like a coffee cake texture inside. I even blogged about it on my own (i used peaches) http://kristenpraz.blogspot.com/2010/09/peach-upside-down-cake.html
I made this cake and used regular salt instead of coarse salt and it turned out much better. Also do not need to cook as long as recommended - only about 40 minutes in my oven.
THIS RECIPE DOES NOT WORK! The cake is heavy and when inverted becomes gummy before you serve it even after straining the fruit. The bake ttime is totally to long. It only took 25 minutes for a 1 layer cake. This recipe is a total waste of ingredients and should have been tested before printing. CANNOT RECOMMEND..