Position a rack in the center of the oven and preheat to 350 degrees F. Grease the bottom and sides of a 10 x 3-inch round cake pan (don't use a springform pan, or the caramel might leak out during baking). Line the bottom of the pan with a round of parchment paper and grease the paper.
Sift together 1 ½ cups flour, 1 ½ teaspoons baking powder, ¼ teaspoon baking soda, ½ teaspoon cinnamon, ½ teaspoon ginger and ¼ teaspoon salt into a medium bowl, whisk to combine and set aside.
In a small bowl, stir together 1 cup sour cream and 2 teaspoons vanilla extract; set aside.
In a mixing bowl, beat 9 Tablespoons butter at medium-high speed until creamy, about 1 minute. Gradually add 1 cup sugar and beat at high speed until the mixture is lightened in texture and color, about 2 minutes. Reduce the speed to medium and add 2 eggs one at a time, beating well after each addition and scraping down the sides of the bowl as needed. At low speed, add the flour mixture in three additions, alternating it with the sour cream mixture in two additions and mixing just until blended. (Do not over mix this batter.)
Spoon the batter in large dollops over the peaches, then smooth it into an even layer. Bake for 40-45 minutes, until the cake is golden brown and springs back when lightly touched. Set the pan on a wire rack and cool for 10 minutes.
Run a thin-bladed knife around the edge of the pan. Using pot holder, very carefully invert the cake onto a cake plate or platter. Peel off the parchment paper if it doesn't stay in the pan and re-arrange any peaches that may have become loose or that stayed in the pan. Serve warm or at room temperature.
Store in an air tight container at room temperature up to 2 days, or refrigerate for up to a week. Bring to room temperature before serving.