Preheat the oven to 350 degrees. Coat a 9-inch loaf pan with cooking spray and line with parchment paper, allowing the paper to hang over the sides. If you don't have parchment paper, coat your pan with cooking spray and then dust with flour.

In a large bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set aside.

In medium bowl, whisk together the eggs and sugar. Whisk in the melted butter, heavy cream, and vanilla.

Add the wet ingredients to the flour mixture and whisk to combine. When almost completely blended, whisk in the boiling water.

Transfer the mixture to the prepared pan and bake for 40-42 minutes, until a wooden pick comes out clean or with little moist bits clinging to it.

Cool the cake in the pan, on a wire rack, for 20 minutes. Remove loaf from the pan and cool, on a wire rack, for at least 20 minutes before slicing.