Preheat your oven to 350°F (175°C) and prepare a 9x13-inch baking pan by greasing it or lining with parchment paper.

In a large mixing bowl, combine 2 cups of all-purpose flour, 1 cup of granulated sugar, 1 teaspoon of cinnamon, and ½ teaspoon of salt. Cut in 1 cup of softened unsalted butter until it resembles coarse crumbs. Add in 1 egg and ½ cup of brown sugar, mixing until just combined.

Press about two-thirds of the crust mixture into the prepared baking pan and bake for 10 minutes until golden.

Slice 4 cups of fresh peaches and combine them with ½ cup of granulated sugar and 1 tablespoon of lemon juice in a mixing bowl, tossing gently.

Spread the peach mixture evenly over the crust. Crumble the remaining crust mixture over the peaches, and bake for an additional 25 to 30 minutes.

Once done, cool the bars in the pan on a wire rack for at least 30 minutes before slicing.