1. Butter and flour-dust a 10-inch decorative tube pan.
2. In a small bowl, mix poppy seed, buttermilk, and almond extract.
3. In a deep bowl, beat egg whites with a mixer on high until foamy. Continue beating and gradually add 1/4 cup sugar. Beat until whites hold stiff, shiny peaks.
4. In another bowl, using unwashed beaters, beat 1 cup butter and 1 1/2 cups sugar on high speed until light and fluffy. Add egg yolks and beat until well blended. Stir in poppy seed mixture.
5. Mix 2 1/2 cups flour, baking powder, baking soda, and salt.
6. Add dry ingredients to batter; beat slowly to blend. Mix at medium speed.
7. Fold in beaten whites until blended.
8. Mix 1/4 cup sugar and cinnamon. Pour half the batter into pan. Sprinkle with half the cinnamon mixture. Add remaining batter and sprinkle with remaining cinnamon mixture. Holding a knife vertically, draw blade through batter around tube.
9. Bake in 350° oven just until cake springs back when lightly pressed in center, 1 to 1 1/4 hours.
10. Cool in pan 15 minutes. Invert cake onto a plate. Serve warm or cool.