Prepare Oven and Pans: Preheat oven to 350°F (175°C). Grease and flour two 8-inch or 9-inch round cake pans. (Optional: Line bottoms with parchment paper after greasing).

Make Cake Batter: In a medium bowl, whisk together flour, baking soda, salt, and optional cinnamon. Set aside. In a large bowl, beat softened butter, granulated sugar, and brown sugar on medium-high speed for 3-4 minutes until light and fluffy. Add eggs one at a time, beating well after each. Mix in mashed bananas, buttermilk, and vanilla (mixture may look curdled – this is normal). Add dry ingredients in two batches, mixing on low speed only until just combined. Gently fold in chopped walnuts.

Bake the Cakes: Divide batter evenly between the prepared pans. Bake for 30-35 minutes, until a toothpick inserted into the center comes out clean. Let cakes cool in pans for 15 minutes, then invert onto a wire rack to cool completely.

Make Soft Cream Frosting: In a large bowl, beat softened cream cheese and butter on medium-high speed for 2-3 minutes until smooth and creamy. On low speed, gradually add sifted powdered sugar. Add vanilla and salt. Beat on medium-high for 2-3 minutes. Add 2 tablespoons of milk/cream and beat again. Add more milk, 1 teaspoon at a time, until the frosting reaches a thick but pourable consistency (like thick glaze or soft pudding).

Assemble the Cake: Toss sliced bananas gently with lemon juice. Place one completely cooled cake layer on a serving plate. Spread about 1/3 of the frosting evenly over the top. Place the second cake layer on top. Pour the remaining 2/3 of the frosting onto the center of the top layer, gently nudging it toward the edges to allow it to drip naturally down the sides. Immediately arrange the lemon-tossed banana slices and walnut halves on top.

Chill Before Serving (Recommended): Refrigerate the assembled cake for at least 30-60 minutes to help the soft frosting set before slicing.