Coat an 8 x 4-inch loaf pan with cooking spray; sprinkle with 1 tablespoon granulated sugar. Set pan aside. Place flaxseed in a blender or clean coffee grinder, and process until ground to measure about 6 tablespoons flaxseed meal; set aside.
Combine 1 cup granulated sugar and eggs in a large bowl; beat at high speed of a mixer 3 minutes or until mixture is thick and pale. Lightly spoon flour into dry measuring cups; level with a knife. Combine flaxseed meal, flour, baking powder, baking soda, and salt; stir well with a whisk. Combine buttermilk, oil, rind, and vanilla. Add flour mixture to egg mixture alternately with buttermilk mixture, beginning and ending with flour mixture.
Spoon batter into prepared pan. Bake at 350° for 55 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 5 minutes on a wire rack; remove from pan. Cool completely on wire rack.
Combine powdered sugar and lemon juice; drizzle over top of loaf.