Preheat oven to 350F degrees.
Butter a loaf pan and set aside.

In a medium bowl, sift together both flours, baking soda, cinnamon, and salt.

In a large bowl, beat sugar, eggs, and oil until light and fluffy. Stir in mashed bananas, vanilla and greek yogurt.

Fold in dry ingredients and nuts if using.
Pour batter into prepared loaf pan and bake about 45 minutes or until a toothpick inserted into the center of bread comes out clean.

Remove, let cool, and serve