1. Preheat the oven to 350°F (180°C). Grease a 9×5 inches (23x13cm) loaf pan lightly and with a piece of baking parchment. Set aside.

2. For the cream cheese filling mix the cream cheese with flour, sugar, the egg, and vanilla extract until well combined. Set aside.

3. For the batter mash the bananas, add to a large bowl, and mix with the buttermilk, melted butter, eggs, and vanilla extract until well combined. Mix the flour with sugar, baking soda, and salt and add to the large bowl – mix until just combined. Add about 3/4 of the chopped walnuts and fold in, keep the rest for the decoration. Pour about 1/3 of the batter into the prepared loaf pan, then add about 1/2 of the cream cheese filling on top (try to keep it in the center), spoon another 1/3 of the batter on top to cover the filling, then repeat the layering with the remaining cream cheese filling and batter. Cut the banana lengthwise in half and place on top of the batter, sprinkle with the remaining chopped walnuts and bake for 65-75 minutes or until a wooden skewer inserted into the center comes out clean. If the top gets too dark during baking, cover with a piece of aluminum foil and continue baking. Take the finished cake out of the oven and let cool down inside the pan for about 15 minutes, then remove from the pan and let cool down completely on a wire rack.