Preheat the oven to 350°F. Grease the bundt pan and dust it with flour.
In a stand mixer, beat room temperature butter, granulated sugar, and brown sugar until light and creamy (about 3-5 minutes). Add vanilla extract and eggs, mixing slowly.
Pour in room temperature buttermilk and mix. Add flour, baking soda, and salt, mixing on low speed until the batter comes together.
Peel bananas, mash them, and add to the mixer on low speed. Mix until just combined (about 30 seconds).
Pour batter into the prepared bundt pan and bake for 45-55 minutes or until a toothpick comes out clean.
Let the cake cool for 15 minutes before flipping onto a plate or cake stand.