Preheat your oven to 350°F (175°C) and line an 8x8-inch baking dish with parchment paper.
In a bowl, mix flour and ¼ cup granulated sugar. Cut in softened butter until crumbly. Press into the prepared dish.
Bake the crust for about 15 minutes until golden brown.
In another bowl, whisk together eggs, remaining sugar, lemon zest, lemon juice, and lavender until smooth.
Pour the filling over the baked crust and bake for an additional 20-25 minutes until set but slightly jiggly in the center.
Let cool completely before slicing into squares and dusting with powdered sugar.