Preheat the oven to 350° degrees F. Liberally butter a 9 inch cake pan.
Sift together the flour, baking powder, and salt.
Cream together the butter, sour cream, and orange zest.
Slowly add the sugar, mixing until the mixture is light and fluffy. Scrape down the sides of the bowl. Add the eggs, one at a time, mixing well between additions and scraping down the sides.
Add the sifted dry ingredients alternately with the orange juice to the creamed mixture, beating well on low speed after each addition.
Add of layer of alternating orange slices at the bottom of the pan.
Pour batter about half way up in the pan.
Bake until a toothpick inserted in the middle comes out clean, about 35 min.
Cool the cake layer in the pans for 10 min. Loosen the layers by running a knife between the cake and the edge of the pan. Invert onto a rack to cool.