In a medium saucepan over medium heat, melt 4 tablespoons of butter and 1 cup of brown sugar together until bubbly and smooth, about 2-3 minutes. Carefully remove from heat and immediately arrange sliced peaches in the pan, creating a beautiful design to form the topping for your Peach Upside-Down Cake.

Using a stand mixer or handheld mixer, cream together ½ cup softened butter and 1 cup granulated sugar on medium speed for about 3 minutes until fluffy and pale. Add in 2 eggs, one at a time, making sure to fully incorporate the first before adding the next. Mix in 1 teaspoon of vanilla extract for a delightful boost of flavor.

In a separate bowl, sift 1 ½ cups all-purpose flour, 2 teaspoons baking powder, and ½ teaspoon salt. Gradually add this to the butter mixture, alternating with ½ cup milk. Mix on low speed until just blended, being careful not to overmix.

Pour the batter evenly over the caramelized peaches in the pan, ensuring you cover all the peach slices. Gently spread the batter with a spatula to achieve an even layer, taking care not to disturb the caramel topping underneath.

Preheat your oven to 350°F (175°C) and place the cake in the middle rack. Bake for 35-40 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.

Once the cake is baked, remove it from the oven and let it cool in the pan for about 10 minutes. Carefully run a knife around the edges to loosen the cake, then place a serving plate on top. Quickly and confidently invert the pan to release the cake.

Your Peach Upside-Down Cake is best enjoyed warm or at room temperature. Serve it with a scoop of vanilla ice cream or a dollop of whipped cream on top.