For the Topping:

1. PREHEAT THE OVEN: Preheat the oven to 350 degrees.
2. PREP THE PAN: Prepare a 9-inch cake pan by buttering the pan (or using a cooking oil spray), then adding parchment paper to the base of the pan, and then buttering or spraying the parchment paper. Set aside.
3. MAKE CARAMEL SAUCE: Melt the butter in a small saucepan. Add the brown sugar and then simmer, over medium heat, stirring, until sugar is completely dissolved, about four minutes. Then swirl in the salt. 
4. POUR INTO PAN:  Remove from the heat and pour into the prepared pan.
5. ADD PEACHES: Arrange the peach slices on top of the caramel sauce. Set aside.

For the Cake:

1. COMBINE DRY INGREDIENTS: Sift together the flour, baking powder, nutmeg, and salt in a medium bowl. Set aside.
2. CREAM BUTTER AND SUGAR: In another medium bowl or a stand mixer, beat together the butter and the sugar. 
3. ADD EGGS: Beat in the eggs, one at a time.
4. ADD FLOUR MIXTURE: Stir in the flour mixture until combined.
5. BAKE: Pour the batter into the cake pan, spreading evenly over the caramel and peaches, and bake the cake for 30-35 minutes, until the cake is set and golden brown.
6. COOL AND REMOVE FROM PAN: Remove from the oven and set on a cooling rack. Allow the cake to sit for at least 10 minutes. Then run a knife around the sides of the cake to ensure it is not stuck to the pan. Place your cake plate on top of the pan and invert the cake onto the plate. The cake should slide out easily but if any peach slices stick to the pan, just remove them carefully and add them back to the top of the cake.
7. SERVE: Serve warm or at room temperature. Add a topping like ice cream or fresh whipped cream, if desired.