Preheat your oven to 350°F (175°C). Grease your bundt pan with butter or cooking spray to prevent sticking.

In a large mixing bowl, cream together the softened butter and brown sugar until light and fluffy. Add the eggs one at a time, mixing well after each addition. Stir in the mashed bananas and vanilla extract until thoroughly combined.

In another bowl, whisk together the all-purpose flour, baking soda, and salt.

Gradually add the dry ingredient mixture into the wet ingredients, alternating with the buttermilk. Begin and end with the flour mixture, mixing gently until just combined. Avoid overmixing.

Pour the batter into your prepared bundt pan, smoothing the top with a spatula to ensure an even bake.

Place the bundt pan in the preheated oven and bake for 50-60 minutes or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for about 15 minutes before inverting it onto a wire rack.

For the glaze, in a small saucepan over medium heat, combine brown sugar, butter, and milk. Stir until boiling, then remove from heat and let cool slightly before drizzling over the cooled cake.