Spray and flour a bundt pan (or a tube pan with a removable bottom)
Heat the poppy seed in the milk in a saucepan until almost boiling. Add the buttermilk, juice, zest and vanilla beans and set aside to cool. Cream the butter and sugar until fluffy. Add the eggs one at a time, beating in between.
Mix the flours, baking powder, soda and salt together in a separate bowl.
Add the dry ingredients to the butter mixture alternately with the wet. Beat just until blended with each addition.
Pour the batter into the cake pan and bake for about 50-55 minutes or until a toothpick comes out clean. Leave to cool for about 15 minutes and then carefully turn it out onto a rack.
To make the glaze, add just enough of the tangerine juice to the sugar to make a fairly thick glaze. Add the poppy seeds and extract and stir well.