Preheat the oven to 350 F. Grease and flour (or use a grease/flour combo spray such as Baker's Joy) a 9 inch round cake pan. Set aside.

Whisk together the flour, sugar, baking powder, baking soda, cardamom and salt. Set aside.

Whisk together the yogurt, sour cream, oil, eggs and vanilla. Pour over the flour mixture and gently mix until just evenly moistened.

Scrape the batter into the prepared cake pan and smooth the top. Bake until the top of the cake is golden and a toothpick inserted into the center of the cake comes out clean or with only a few crumbs attached, about 40 minutes.

Let the cake cool in the pan for 5 minutes, and then turn out onto a plate. Flip the cake onto a cooling rack lined with wax paper so that the golden top of the cake is again the top. Let cool completely before slicing. Serve with confectioners' sugar or whipped cream.