4 peaches, peeled and sliced
1/4 cup sugar
1 1/2 sticks unsalted butter at room temperature
1 1/3 cups sugar
3 eggs at room temperature
1 1/2 tsp. grated orange zest
2 tsp. vanilla
2 1/3 cups cake flour (sifted, then measured)
1 1/2 tsp. baking powder
1/2 tsp. salt
1/2 tsp. baking soda
1 cup of buttermilk
Butter a 9" diameter springform pan. Cut a piece of parchment paper to fit the bottom and butter that. Dust the pan with flour. Place pan on a baking sheet.
Preheat oven to 350 degrees F.
Mix sliced peaces with 1/4 cup sugar in a bowl and allow to rest for a few minutes. Arrange peach slices in bottom of springform pan.
Cream butter and sugar in a mixer until it is light and fluffy. Add eggs one at a time until incorporated. Add orange zest and vanilla and mix in.
Mix the 2 1/3 cups of sifted cake flour with the baking powder, salt and baking soda. Sift into a bowl to be sure the baking powder and soda are evenly distributed.
On low speed add the flour mixture and buttermilk to the batter in 3 additions alternating the flour and the buttermilk.
Pour the batter over the peaches and smooth the top. Bake until the cake is golden brown and a tester inserted in the center comes out clean, about 1 hour and 20 minutes. Let cool in pan set on a wire rack for about 15 minutes. Invert onto a cake plate, loosen the sides of the springform pan and remove it and the bottom piece. Peel off the parchment paper. Dust with powdered sugar and serve