Creating the Brown Butter Apple Upside Down Cake can be a joyous process when you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan and line the bottom with parchment paper for easy release.

2. Brown the Butter: In a small saucepan, melt the unsalted butter over medium heat. Continue to cook until it becomes golden brown and nutty, about 5-7 minutes. Watch closely to avoid burning. Remove from heat and allow it to cool slightly.

3. Prepare the Apples: In a medium bowl, mix sliced apples with brown sugar and cinnamon. Set aside to let them macerate while you prepare the batter.

4. Mix Dry Ingredients: In another bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.

5. Combine Wet Ingredients: In a large mixing bowl, whisk together the granulated sugar and browned butter. Add the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract.

6. Add Dry Ingredients: Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk. Mix gently until just combined, ensuring not to overmix.

7. Assemble Cake: Pour the browned butter and apple mixture into the bottom of the prepared cake pan. Then, pour the cake batter over the apple mixture, spreading it out evenly.

8. Bake: Place the pan in the preheated oven and bake for 40-45 minutes or until a toothpick inserted in the center comes out clean.

9. Cool: Once baked, remove the cake from the oven and let it cool in the pan for about 10-15 minutes. Then, invert the cake onto a serving plate carefully.

10. Serve: Allow the cake to cool further before slicing. Enjoy it warm, at room temperature, or chilled, as desired.