Preheat your oven to 350°F (175°C) and prepare your baking pan by greasing it lightly.

In a mixing bowl, combine flour, powdered sugar, and salt. Cut in cold butter until mixture resembles coarse crumbs. Press into prepared pan and bake for 15-20 minutes until golden.

Prepare lavender syrup by boiling water, adding sugar and lavender, stirring until dissolved. Let steep and cool for 10 minutes, then strain.

In a bowl, whisk together eggs and cooled syrup until smooth. Mix in lemon juice and zest, then stir in flour and sugar until smooth.

Pour filling over baked crust and return to oven. Bake for 20-25 minutes until filling is set but with a slight jiggle.

Let bars cool to room temperature, then refrigerate for at least 2 hours before cutting into squares and garnishing with lavender and lemon slices.