Preheat your oven to 350°F (175°C) and grease a 9" x 13" baking pan.

In a mixing bowl, combine flour, sugar, and salt. Cut in the diced butter until the mixture resembles coarse crumbs. Press the dough evenly into the bottom of the prepared pan and bake for 20 minutes until lightly golden.

Whisk together sugar and flour in another bowl, then add eggs, lemon zest, and lemon juice, stirring until smooth.

Pour the custard mixture over the baked shortbread base. Bake for an additional 20 to 25 minutes until set but still slightly wobbly in the center.

Let the bars cool at room temperature for about 30 minutes, then refrigerate for at least 2 hours.

Dust with powdered sugar and garnish with fresh dandelion petals before serving.