Step 1

Preheat the oven to 375 degrees F (190 degrees C). Coat an 8x8-inch baking pan with cooking spray.

Step 2

Whisk flour, sugar, baking powder, and salt together in a bowl. Next, cut in the cold butter using 2 forks or a pastry cutter then slowly mix in the egg yolk and cold water. Don't worry if the dough seems really crumbly; it should be!

Step 3

Press 1/2 of the crumble mixture into the prepared pan to make the crust. Save the rest for the top of the bars.

Step 4

Stir together peach slices, sugar, flour, lemon juice, vanilla extract, cinnamon, and nutmeg until combined. Evenly add peach filling to the top of the crust.

Step 5

Sprinkle the remaining crumble over the peach filling.

Step 6

Bake in the preheated oven until golden brown and set, 30 to 38 minutes. Cool bars to room temperature, then cut and serve.