Mix dry ingredients, including poppy seeds and set aside.In a small bowl, mix bananas and buttermilk. Set aside.
Mix butter and sugar with the electric mixer until fluffy. Add eggs,one at the time. Add half of the flour mixture,the banana mixture,and then the rest of the flour. Mix only until combined. Be careful not to over mix.
Pour dough to greased and floured bundt cake pan. Bake in a 350 F preheated oven for 45-50 minutes.Let it cool before taking it out of the pan.
Sprinkle with powdered sugar or glaze with chocolate frosting.I did and it tastes fabulous.