STEP 1: Preheat the oven to 350°F. Butter a bundt pan and dust on some flour, dumping any extra flour out. In a medium bowl, sift together flour, baking powder, baking soda, and salt. Set aside.
STEP 2: In the large bowl of a stand mixer (or with an electric mixer) cream together the butter and sugar until light and fluffy. Should take 3-4 minutes at medium speed.
STEP 3: Add eggs in one at a time, scraping the bowl down as needed. Continue to beat for 5 minutes. Then mix in vanilla extract and zest.
STEP 4: Add in 1/3 of the flour mixture, alternate adding in buttermilk with the orange juice. Once completely mixed, hand stir in the poppy seeds.
STEP 5: Pour the batter into the bundt pan and bake for 50-60 minutes. The cake should be golden brown. Check doneness with an electric thermometer it should read 205°F to not be over-cooked. If you don't have a thermometer, use a cake tester or toothpick in the thickest part of cake, it should come out with a few moist crumbs. Let the cake stand for 5 minutes, then remove the cake from the pan and let it cool completely on a wire rack.
STEP 6: While cake is cooling, add the heavy cream to a small heat-proof bowl and microwave for 2 minutes. Add the chocolate and let it sit for 3 minutes. Add in the butter and the zest and stir until the chocolate is melted and smooth.
STEP 7: Move cake from cooling rack to the serving plate. Drizzle the chocolate glaze over the cake and let cake sit for 5 minutes to allow the cake to set or put in the refrigerator for 30 minutes to further harden the chocolate. Serve.