Soak poppyseeds in the buttermilk for 15 minutes.
Cream together butter and sugar.
Add yolks to creamed mixture.
Add almond extract or vanilla.
Add dry ingredients alternately with buttermilk mixture, a little at a time.
Beat egg whites very stiff as for angel food.
Fold egg whites into mixture.
Pour half of this batter mixture into well-greased bundt pan.
Sprinkle with a mixture of about 1/4 cup brown sugar and about 1 teaspoon cinnamon.
Pour in remaining batter.
Bake at 350 degrees for 1 hour.
Cool and invert onto serving dish, then remove bundt pan.
NOTES: When folding in egg whites, be gentle.
Lift and turn the batter instead of using a stirring motion.
Don't worry if a little bit of egg white remains unmixed; the egg whites will collapse if you mix it too much.