Prepare the Eggplant Puree: Melt the butter in a medium saucepan over medium heat. When it foams add the eggplant and salt, turn the heat to medium-high and cook, stirring, until the eggplant starts to soften, about 3 minutes. Add the honey, water, vanilla extract, and pumpkin spice. Continue to cook, stirring occasionally, until the eggplant is soft and caramelized. Allow to cool for a few minutes, then place in a food processor or blender and blend until completely smooth. Set aside and let cool. Heat the oven to 350¯F.
Make the Cake: Butter and flour a 9-inch cake pan shaking to remove excess flour. Set aside.
In a medium bowl combine the flour, cornmeal, baking powder, and salt. Mix with a whisk.
In a large bowl beat together the butter and sugar, using a handheld or stand-up mixer, until they are light and fluffy. Add the eggs, one at a time, and beat until incorporated. Add the vanilla and eggplant mixture, mix well. Add the flour in 2 batches, alternating with the milk, mix until just fully incorporated. Do not over-mix.
Pour the mixture into the prepared pan, using a spatula to make the top even, and place it in the middle third of the oven. Bake until the cake starts to pull away from the side and the top is golden brown, about 35-45 minutes. A toothpick, when inserted into the center, should come out clean.
Set the cake, still in the pan, on a cooling rack and allow to cool for 15 minutes. Invert the cake onto the rack and allow to cool completely.
Prepare the Frosting: When the cake has cooled, prepare the frosting. Using an electric mixer, or whisk, beat the cream until it just begins to thicken, add the confectioner's sugar and beat until soft peaks form. Add the orange zest and extract. Mix well. Frost the top and sides of the cake, cut and serve. This cake will hold, covered in the refrigerator, for up to 2 days.