Preheat oven to 350-degrees.
In a small bowl, whisk together the buttermilk, orange zest, orange juice, and orange extract (optional). Set aside.
Mash the banana with a fork in a small bowl. Set aside.
In a large bowl, whisk together the flour, baking soda, baking powder, and salt. Set aside.
In a large bowl of a stand mixer (or use a hand mixer) cream together the softened butter and sugar until light and fluffy.
Add the mashed banana to the butter and sugar mixture and blend to combine.
Add the buttermilk mixture to the mixing bowl and blend on low speed to combine.
Incorporate the flour mixture (by thirds) into the mixing bowl, blending after each addition.
Add the eggs (one at a time) into the batter blending well after each addition.
Stir in the poppy seeds until well distributed throughout the batter.
Pour the batter into a bundt pan which has been liberally sprayed with baking spray.
Place the cake pan on a baking sheet and bake in a preheated oven for 75-90 minutes, or until a skewer inserted in the center of the cake comes out clean.
Cool the cake on a baking rack for 30 minutes and then turn the cake out onto a serving plate and allow to cool completely before icing.