Step 1: Prepare the Cake Batter

1. Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking pan or line it with parchment paper for easy removal.
2. In a large mixing bowl, whisk together the flour, baking powder, baking soda, and salt until fully combined.
3. In another bowl, mash the ripe bananas using a fork until smooth. Add the brown sugar, granulated sugar, eggs, melted butter, buttermilk, and vanilla extract, and mix until the wet ingredients are well blended.
4. Gradually add the dry ingredients to the wet ingredients, stirring just until combined. Be careful not to overmix, as this can result in a dense cake.
5. Fold in the poppy seeds and walnuts if you’re including them.

Step 2: Bake the Cake

1. Pour the batter into the prepared baking pan and spread it evenly with a spatula.
2. Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
3. Once baked, let the cake cool completely in the pan.

Step 3: Make the Cream Cheese Frosting

1. In a large bowl, beat the softened cream cheese and butter together until smooth and creamy.
2. Gradually add the powdered sugar, mixing on low speed to avoid splattering, then increase to medium-high until the frosting is light and fluffy.
3. Stir in the vanilla extract for an added layer of flavor.

Step 4: Assemble the Cake

1. Once the cake is completely cooled, use a spatula to spread the cream cheese frosting evenly over the top.
2. For garnish, sprinkle with extra chopped walnuts or a light dusting of poppy seeds, if desired.
3. Slice, serve, and enjoy!