Preheat oven to 350 degrees F. Butter or spray with vegetable oil a 10-inch bundt pan.
In a medium bowl, mix together flours, baking soda, salt, and cocoa.
In a second bowl, beat together butter and sugar with an electric hand mixer or stand mixer.
Add eggs, one at a time, beating well.
In a small bowl, whisk together zest, vanilla, yogurt, and orange juice.
Add 1/3 of the dry ingredients to the butter/sugar mixture and mix by hand then add 1/3 of the yogurt mixture and mix by hand. Alternate in this way until all ingredients have been mixed together.
Pour mixture into bundt pan and bake, 50 to 60 minutes, till a knife or toothpick inserted comes out clean.
Allow to cool for 15 minutes before inverting onto a plate or wire rack then continue to cool.
Optional glaze: Add orange juice, sugar, and lemon juice in a small sauce pan over medium-high heat. Bring to a boil then lower heat and simmer, uncovered, for 3 minutes. Pour the hot glaze over the cooled cake and allow to stand for 15 minutes before slicing.