Preheat the oven to 350°F.
Spray your bundt pan with nonstick spray or brush with melted butter, flour it generously especially if the bundt pan has a lot of decorative features. Tap out the excess flour and set aside.
Toast the walnuts in a skillet over medium heat until fragrant and lightly brown, about 3 - 5 minutes. Set aside to cool, then roughly chop or break them up into smaller pieces with your hands.
Make the cheesecake filling: Using an electric hand mixer or a sturdy spatula, beat the softened cream cheese with sugar until creamy and smooth. Add egg, vanilla, cinnamon, and beat until combined. Refrigerate until ready to use.
Make the banana cake batter: Mash the bananas in a bowl using a potato masher. Measure 1 ½ cup of mashed bananas and transfer it into a large mixing bowl. If you weigh your bananas, you can just mash it directly in the mixing bowl and skip the cup measurement.
Add the melted butter, oil, eggs, vanilla extract, and beat until smooth. Add brown sugar and beat to combine.
In another mixing bowl, sift together flour, baking powder, baking soda and cinnamon, stir in the kosher salt and mix until evenly distributed.
Add the flour mixture to the wet ingredients and mix until just combined with a large whisk or spatula. Fold in the chopped walnuts.
Spoon half of the cake batter into the prepared bundt pan, distribute it evenly. Spoon in the cheesecake filling in an even layer, try to avoid the sides of the pan. Add the remaining cake batter on top.
Bake for about 50 minutes until a toothpick inserted comes out clean with just a few crumbs attached.
Set the bundt pan on a wire rack to cool completely before removing the cake. The cake should pull away from the sides as it cools.