Preheat your oven to 350°F (175°C). In a mixing bowl, combine butter and sugar until light and fluffy. Sift in flour and salt, mix until a dough forms. Press into the bottom of a greased baking pan and bake for 20 minutes. Cool slightly.

Warm lemon juice gently in a saucepan, add lavender, and steep for 10 minutes. Strain the mixture. In another bowl, whisk together eggs and sugar until pale. Stir in flour, then the cooled lemon-lavender juice. Ensure everything is combined.

Pour the filling over the crust and bake for 22-25 minutes until set. Allow cooling at room temperature for about an hour.

Refrigerate the bars for at least 2 hours to firm up. Slice into squares carefully.

Dust with powdered sugar before serving and add edible lavender buds if desired.