Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 9-inch round cake pan.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, cream together the butter and sugar until light and fluffy. Add the eggs, one at a time, beating well after each addition. Mix in the vanilla.
Add the cocoa powder and mix until combined. Alternately add the dry ingredients and the buttermilk, starting and ending with the dry ingredients. Mix until just combined.
Stir in the poppy seeds until evenly distributed. Pour the batter into the prepared pan.
Bake for 30 to 40 minutes, or until a toothpick inserted into the center comes out clean. Let cool in the pan for 10 minutes before turning out onto a wire rack to cool completely.
Interesting Facts
Poppy seeds are a popular ingredient in many European baked goods.
This cake is great for a special occasion, like birthdays or anniversaries.
This cake is perfect with a scoop of ice cream or a dollop of whipped cream.