Preheat your oven to 350°F (175°C). In a mixing bowl, combine flour, powdered sugar, and chilled diced unsalted butter. Use a pastry cutter to blend until mixture resembles coarse crumbs. Press this mixture into a 9-inch tart pan and bake for 15-20 minutes until light golden brown.

Whisk together fresh lemon juice, lemon zest, and sugar in a medium bowl. Then add heavy cream and dried lavender, mixing until well combined and sugar is dissolved.

Pour the lemon-lavender filling into the pre-baked tart crust. Bake for 25-30 minutes. The filling should be set but still slightly jiggly in the center.

Allow the tart to cool at room temperature for about 20 minutes, then refrigerate for at least 2 hours to set properly.

Top the tart with fresh edible flowers and whipped cream just before serving. Arrange thin lemon slices if flowers are unavailable.

Slice the chilled tart into wedges and serve. Pair with tea or coffee for a delightful treat.