Preheat your oven to 350°F and grab a 9-inch cast iron skillet. I always use cast iron here because it distributes heat evenly and creates those caramelized edges you'll actually fight over. Melt 1/2 cup unsalted butter in the skillet over medium heat for about 2 minutes until foaming gently. It should smell nutty, not burnt—that's your signal to stop.

Sprinkle the light brown sugar and melted butter evenly over the hot butter base. Stir gently until it becomes a thick, glossy paste that clings to the bottom—this takes maybe 60 seconds. Press the chopped pecans into this mixture in an even layer. They'll toast slightly as the cake bakes, which is exactly what we want.

Arrange your peach slices in a circular pattern over the pecan-sugar mixture. Start from the outside and spiral toward the center like you're creating something beautiful (because you are). I overlap mine slightly so they nestle together and caramelize into a connected golden layer. Leave no gaps because those hot spots will burn.

In a separate bowl, whisk together 1 1/2 cups all-purpose flour, 1/2 tsp baking powder, and 1/4 tsp salt. This combination aerates the dry ingredients, which prevents the batter from becoming dense and heavy. I always sift these three together because lumps in flour are sneaky and ruin texture—trust me, I've learned this the hard way.

In another bowl, cream 1 cup granulated sugar with 2 large eggs until pale and fluffy (about 2–3 minutes with a mixer). This step incorporates air into the batter, which gives the peach upside down cake cozy its tender crumb. Add 1 tsp vanilla extract and beat for another 30 seconds. Vanilla is non-negotiable because it brightens the fruit flavor without tasting vanilla-forward.

Alternate adding the flour mixture and 1/2 cup whole milk to the egg mixture in three additions: flour, milk, flour, milk, flour. Mix gently after each addition until just combined—overmixing creates toughness. Pour this batter slowly over the peaches and pecans, spreading it gently to the edges with a spatula. The batter will seem thin, but that's perfect; it rises and sets during baking.

Bake for 38–42 minutes until the top is golden and a toothpick inserted into the cake (not the peach layer) comes out with just a few crumbs. The skillet handle will be screaming hot, so use an oven mitt. Let the cake cool in the skillet for exactly 5 minutes—any longer and it sticks; any shorter and it falls apart.

Run a thin knife around the edges, then place your serving plate face-down over the skillet. Take a breath, then flip with confidence in one smooth motion. The peaches should stay on top, gleaming with caramel.