Spray your bundt pan with non-stick spray and flour or sprinkle with cocoa powder.
To a large bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.
In another large bowl (or bowl of your stand mixer), beat the butter on medium speed until creamy (30-45 seconds).
Gradually add the sugar while beating on low until blended.
Increase the mixer speed to medium-high and continue beating, scraping down the sides of the bowl as needed, until the mixture is light & fluffy (3-5 minutes).
Add the eggs, one at a time, beating after each addition and making sure they're fully incorporated before adding the next. The mixture will be thick and creamy after 1-2 minutes.
Beat in the vanilla extract.
Reduce speed to low and fold in the flour mixture in three parts, alternating with the sour cream. Flour/sour cream/flour/sour cream/flour. Mix until just blended with no lumps of flour remaining.
Gently fold in the melted chocolate.
Pour the batter into your prepared pan.
Check for doneness after 50 minutes. Some are done at this point. Mine takes closer to 1 hour. A toothpick inserted in the center of the cake should come out clean.
Transfer to a wire rack to cool for 10 minutes.
To make the glaze
While the cake is cooling, to a small saucepan over low heat, add the sugar and water and stir until the sugar is fully dissolved.
Remove from heat and stir in the chocolate liqueur.
Once cooled, flip the cake onto a piece of parchment/wax paper and brush the warm cake with the glaze.
Let cool to room temperature and then dust with powdered sugar before serving.
Make sure you're properly scooping and measuring the flour - spoon into the measuring cup and level off. Don't scoop directly from the bag/container - it packs in too much flour.Use regular unsweetened cocoa powder (like Hershey's). Start with room temperature butter, eggs, and sour cream for best results.