Step 1: Prepare the Crust

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 9×9-inch baking pan or line it with parchment paper for easy removal.
2. Mix Dry Ingredients: In a medium bowl, combine 1 3/4 cups of flour, 3/4 cup granulated sugar, salt, and baking powder.
3. Cut in Butter: Add the cold butter pieces to the flour mixture. Use a pastry cutter or your fingers to mix until the mixture resembles coarse crumbs.
4. Press into Pan: Reserve about 1 cup of the crumb mixture for the topping. Press the remaining mixture firmly into the bottom of the prepared pan to form the crust.

Step 2: Make the Lemon Filling

1. Whisk Filling Ingredients: In a separate bowl, whisk together 1 cup granulated sugar, eggs, lemon juice, lemon zest, 1/4 cup flour, and 1/2 teaspoon baking powder until smooth and well combined.
2. Pour Over Crust: Pour the lemon filling over the prepared crust in the baking pan.

Step 3: Add the Topping

1. Sprinkle Reserved Crumbs: Take the reserved crumb mixture and sprinkle it evenly over the lemon filling.

Step 4: Bake

1. Bake: Bake in the preheated oven for 25–30 minutes, or until the topping is golden brown and the filling is set. A toothpick inserted should come out clean.
2. Cool: Allow the bars to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.

Step 5: Serve

1. Dust with Powdered Sugar: Once cooled, dust the top with powdered sugar before cutting into squares.
2. Enjoy: Serve chilled or at room temperature.