Preheat the oven to 350 degrees F. Butter and flour a bundt pan.
- Mix together the flour, baking powder, baking soda and salt. Combine the yogurt, citrus zest and vanilla.
- Cream the sugar and the egg, add the oil. Alternately add the flour mixture with yogurt, and mix until just combined, being careful not to over mix.
- Pour the batter into the prepared pan and bake for 50-55 minutes or until a toothpick comes out clean. Cool in pan on a rack for 10 minutes.
- Sprinkle the cooled cake with confectioners’ sugar if desired, and serve with orange or lemon slices.