Preheat oven to 275 degrees F (140 degrees C). Grease and flour a 12 cup non-stick bundt pan, or spray with non-stick baking spray.
Zest and juice the Lemon (1). Mash the Banana (4). Soften the Unsalted Butter (3/4 cup).
In a small bowl, mix overripe bananas, lemon zest, and lemon juice. Set aside.
In a medium bowl, mix All-Purpose Flour (3 cup), Baking Soda (1 1/2 teaspoon), and Salt (1/2 teaspoon). Set aside.
In a large bowl, cream unsalted butter and Granulated Sugar (1 3/4 cup) until light and fluffy, about 3 minutes. Add large Egg (3), one at a time, incorporating each before adding the next. Stir in Vanilla Extract (2 teaspoon).
Blend 1/3 of flour mixture and then add 1/3 Buttermilk (1 1/2 cup) until just blended. Alternate flour and buttermilk until batter is just combined, but be careful not to overbeat. Add banana mixture to batter and mix until just combined.
Pour batter into prepared pan and bake in preheated oven for 1 hour and 40 minutes, or until a toothpick inserted in the center of cake comes out clean.
Transfer the cake from the oven directly to the freezer (still in the pan) for 45-60 minutes.
After cooling in the freezer, transfer cake to a cooling rack for at least 3 hours.
Meanwhile, prepare the ganache. Heat Heavy Cream (1/2 cup) in a small saucepan over medium heat, until hot, but not boiling. While heavy cream is heating, finely chop Semi-Sweet Chocolate Chips (4 ounce) on a cutting board and transfer to a bowl.
Pour hot heavy cream over chocolate and let sit for a few minutes until chocolate softens. Use a whisk to carefully incorporate the heavy cream into the semi-sweet chocolate until glistening and smooth.
Invert the cake onto a cake plate or pedestal. Spoon ganache over the cooled cake so that it runs over the ridges. Store cake, covered, in refrigerator for up to 3 days.