Melt 3 tablespoons butter in round 9-inch oven-safe skillet or cake pan.
Sprinkle brown sugar evenly over butter. Arrange nectarine wedges in circular pattern over brown sugar.
Combine remaining butter and granulated sugar in mixer bowl; mix thoroughly.
Add egg and liqueur and mix 3 to 4 minutes until light and fluffy.
Combine flour, baking powder and salt; mix well.
Add flour mixture and milk to butter mixture alternately, starting and ending with flour mixture; mix only until smooth. Spoon batter over nectarines.
Bake at 350ºF about 45 minutes or until wooden pick inserted near center comes out clean.
Loosen edges and place serving plate over pan.
Carefully turn upside down on serving plate. Remove pan. Garnish with lavender blossoms if desired and serve warm.