Mix 1/2 cup sugar, flour and salt in top of double boiler. Blend in 3 egg yolks and milk. Cook, uncovered, over boiling water, stirring constantly for 10 to 12 minutes or until thickened. Remove from heat; stir in vanilla and Coconut.
After pudding has cooled either pour into cooled pre-baked pie crust or ovenproof bowl.
Beat egg whites until soft peaks form; gradually add remaining 1/4 cup sugar and beat until stiff but not dry. Spoon on top of pudding, spreading evenly to cover entire surface and sealing well to edges.
Bake at 350°F in top half of oven for 15 to 20 minutes or until browned. Cool slightly or refrigerate.