Preheat oven to 350°F (180°C).
In a medium bowl, whisk together flour, salt, baking powder, cinnamon, and baking soda.
In a large bowl, whisk together sugars and eggs. Add banana, oil, buttermilk, and vanilla, whisking until combined. Add flour mixture, and whisk until just combined and no dry spots remain.
Spoon 1⁄2 cup (168 grams) hazelnut chocolate spread into a pastry bag, and cut a 1⁄4-inch opening in tip.
Spray a Nordic Ware 6-Cup Charlotte Cake Pan with baking spray with flour. Spoon two-thirds of batter (about 12⁄3 cups or 503 grams) into bottom of prepared pan, spreading to edges. Pipe hazelnut chocolate spread evenly over batter, leaving a 1⁄4-inch border around edges. Using a wooden pick or skewer, level hazelnut chocolate spread and lightly swirl into batter. Top with remaining batter, spreading to edges. Firmly tap pan on a kitchen towel-lined counter to settle batter. Using a wooden pick or skewer, swirl batter.
Bake until a wooden pick inserted in center comes out with a few moist crumbs, 30 to 35 minutes. Let cool in pan for 10 minutes. Remove from pan, and let cool completely on a wire rack.
In a small microwave-safe bowl, combine cream, butter, and remaining 1⁄4 cup (84 grams) hazelnut chocolate spread. Heat on high in 30-second intervals, stirring between each, until butter is melted and hazelnut chocolate spread has softened. Whisk until combined. Spread ganache over cooled cake. Refrigerate in an airtight container for up to 3 days.