Preheat your oven to 350°F (175°C).

Grease a 9x13 inch baking pan with butter or line it with parchment paper.

In a mixing bowl, combine the flour, sugar, softened butter, salt, and baking powder.

Mix until it resembles coarse crumbs.

Press about two-thirds of the crust mixture into the bottom of the prepared pan.

In another bowl, toss the sliced peaches with lemon juice, cornstarch, vanilla extract, and optional cinnamon.

Spread the peach filling evenly over the crust in the pan.

Sprinkle the remaining crust mixture over the peach filling.

Bake for 30 to 35 minutes or until the top is golden brown.

Allow the bars to cool completely in the pan before slicing.