Preheat oven to 350°. In a small bowl, cream butter and confectioners' sugar. Add the flour, almonds, lavender and lemon zest; beat until crumbly. Pat into an ungreased 13x9-in. baking dish. Bake for 15 minutes or until edges are golden brown.
Meanwhile, in another small bowl, combine the sugar, flour, baking soda, eggs and lemon juice; beat until frothy. Pour over hot crust. Return to oven and bake 20-25 minutes or until light golden brown. Cool on a wire rack. Dust with confectioners' sugar. Refrigerate leftovers.
Look for dried lavender flowers in spice shops. If using lavender from the garden, make sure it hasn't been treated with chemicals.