Preheat your oven to 325°F. In the bowl of your stand mixer fitted with the paddle attachment, cream together the butter and brown sugar on medium speed for about 2 minutes, until fluffy and smooth.
Add the eggs, one at a time, then stir in vanilla, mashed bananas, a pinch of salt, baking powder, and baking soda, mixing just until everything is combined.
Don’t forget to scrape down the sides of the bowl so nothing gets left behind.
Turn your mixer to low and gently fold in the flour until just incorporated. Finally, stir in the walnuts so they’re evenly scattered throughout the batter.
Generously coat a 10-cup bundt pan with baking spray and pour in the batter, smoothing the top lightly.
Bake for 70 minutes, until the cake is set and a toothpick inserted in the center comes out clean. If it starts browning too quickly, loosely tent it with foil to prevent over-browning.
Once baked, let the cake cool in the pan for about 20 minutes. Run a butter knife carefully around the edges, then invert the cake onto a platter or wire rack to cool completely.
While the cake cools, make the glaze. In a small saucepan, combine butter, sugar, salt, vanilla, and heavy cream over medium heat.
Stir constantly as the mixture melts, then bring it to a gentle boil and let it simmer for 2 minutes.
Allow the glaze to cool for about 5 minutes before pouring it over the cake.
As the glaze drips down the sides, use a spoon to drizzle any extra back on top so the cake is fully coated and glistening.
You can also pour the glaze over the cake while it’s still in the pan if you prefer a little trick for easier cleanup.