Preheat your oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper or lightly grease.

In a large mixing bowl, whisk together 2 cups of all-purpose flour, 1 cup of brown sugar, 0.5 cup of granulated sugar, 1 teaspoon of baking powder, 1 teaspoon of ground cinnamon, 0.5 teaspoon of ground nutmeg, and 0.25 teaspoon of salt.

Cut 0.5 cup of cold, unsalted butter into the dry mixture until it resembles coarse crumbs.

Add 1 large egg to the mixture and stir until just combined.

Press the bottom half of the mixture into the prepared baking pan and bake for 15 minutes.

In a separate bowl, combine 4 cups of chopped peaches, 0.5 cup of granulated sugar, 3 tablespoons of cornstarch, 1 tablespoon of lemon juice, and a sprinkle of cinnamon.

Spoon the peach filling onto the baked crust and spread it evenly.

Sprinkle the remaining crumb mixture over the peach filling.

Bake for 40–50 minutes until lightly browned and bubbling around the edges.

Allow the bars to cool completely before slicing into squares.