Prepare Lavender Sugar. Preheat oven to 325 degree F. Let eggs, the 1 cup butter, and sour cream stand at room temperature for 30 minutes. Meanwhile, grease and flour two 8x4x2-inch loaf pans; set aside. In a medium bowl stir together the flour, baking powder, baking soda, and salt; set aside.
In a large bowl beat the Lavender Sugar, granulated sugar, 1 cup butter, and vanilla with an electric mixer on high speed until very light and fluffy, about 4 minutes, scraping down sides frequently.
Add the eggs, one at a time, beating on medium speed about 20 to 30 seconds after each addition.
Alternately add flour mixture and sour cream to butter mixture, beating on low speed after each addition until just combined. Stir in lemon peel. (Batter will be thick.) Stir in lemon peel. Spread mixture in the prepared pans. Bake about 45 minutes or until a wooden toothpick inserted near center comes out clean. Cool on wire rack 10 minutes. Remove from pans and cool completely.
In a small bowl mix powdered sugar with 1 tablespoon melted butter and enough lemon juice to make of drizzling consistency. Spoon over cake, letting some of it drip down the sides. Makes 24 servings (two 8-inch loaves).
In a spice grinder or food processor, grind sugar with dried lavender blossoms.