Preheat oven to 350°.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, 3 tablespoons sugar, and nutmeg in a small bowl; cut in butter with a pastry blender or 2 knives until mixture resembles coarse meal. Firmly press mixture into bottom of an 8-inch square baking pan. Bake at 350° for 12 minutes.
While crust is baking, combine 2/3 cup sugar and next 4 ingredients, stirring with a whisk until blended. Remove crust from oven. Pour lemon mixture over warm crust.
Place fruit spread in a small microwave-safe bowl; microwave at HIGH 30 seconds or until melted. Drizzle over lemon mixture. Bake at 350° for 22 minutes or until very lightly browned around edges. Cool completely on a wire rack. Sift powdered sugar evenly over top.