Preheat your oven to 175°C (350°F). Mix the all-purpose flour, powdered sugar, and salt in a bowl. Add the cold, cubed unsalted butter and blend until the mixture resembles coarse crumbs. Press this buttery mixture into the base of a parchment-lined baking pan, creating an even layer. Bake for about 20 minutes until golden and crisp, setting the stage for the luscious filling.

In a separate bowl, whisk together granulated sugar, cornstarch, lemon zest, lemon juice, eggs, and baking powder. Mix until smooth, with no lumps remaining. The filling should be bright, tangy, and rich with lemon flavor. Pour this over the warm crust, spreading evenly. Return to the oven and bake for an additional 20-25 minutes, until the filling is firm and golden around the edges.

Cool the lemon bars completely before dusting them generously with powdered confectioners sugar. For an added touch, you might drizzle a little extra lemon juice or make a quick glaze by mixing powdered sugar with lemon juice. Slice into squares and serve these vibrant, crowd-pleasing bars chilled or at room temperature, garnished with fresh herbs or berries for extra zing!