Preheat oven to 350 degrees F. Grease and flour a Bundt pan
I a large bowl combine the sugar and orange zest. Rub the zest and sugar between your fingers to release the oils in the zest.
Add the butter, using an electric mixer beat until fluffy. Add the eggs one at a time beating after each addition.
Sift together the flour, baking powder, baking soda, and salt. Combine the orange juice and buttermilk.
Alternate adding the flour mixture and liquid ingredients. Start with the flour and end with the flour.
Pour the batter into the prepared Bundt cake pan. Bake cake for 45 to 50 minutes or until a toothpick inserted comes out clean.
Remove the cake from oven and cool for about 5 minutes before removing the cake from the pan. Set on a cooling rack and to cool
Orange syrup - Combine the 1/3 cup sugar and 1/4 cup orange juice. Stir until the sugar dissolves. Pour over the cake once it is removed from the Bundt pan. Cool completely.
Icing - Once the cake is cooled, combine the powdered sugar and poppy seeds, and gradually add enough orange juice to get the right consistency for drizzling over the cake.