01 - Preheat the oven to 350°F. Line a 9x9-inch baking pan with parchment paper, leaving an overhang on two sides for easy removal of the bars later.
02 - In a mixing bowl, cream together the softened butter and sugar until light and fluffy. Add the flour and salt, mixing until just combined and a crumbly dough forms.
03 - Press the dough evenly into the bottom of the prepared pan. Bake for 18-20 minutes, until lightly golden around the edges. Remove from oven and set aside to cool slightly.
04 - In a large bowl, whisk together the eggs and sugar until pale and smooth. Add the lemon zest, lemon juice, crushed lavender, flour, heavy cream, and a pinch of salt. Whisk until the mixture is fully combined and smooth.
05 - Pour the filling over the slightly cooled crust. Return to the oven and bake for 18-20 minutes, until the center is just set with a slight jiggle—like custard.
06 - Let the bars cool completely in the pan, then refrigerate for at least 1 hour until fully chilled and firm.
07 - Lift the bars from the pan using the parchment overhang. Dust generously with powdered sugar and cut into 16 squares before serving.