In a large saucepan, combine the sugar flour and salt. Stir in water until smooth. Cook and stir over medium-high heat until thickened and bubbly. Reduce heat; cook and stir 2 minutes longer. Remove from the heat. Stir a small amount of hot filling into egg yolks; return all to pan, stirring constantly. Bring to a gentle boil; cook and stir 2 minutes longer. Remove from the heat. Gently stir in the juices and orange and lemon peel. Cool to room temperature without stirring.
Pour into pastry shell. Cool on a wire rack for 1 hour. Chill at least 3 hours.
In a large heavy saucepan, combine the sugar, egg whites, water, cream of tartar and salt over low heat. With a hand mixer, beat on low speed for 1 minute. Continue beating on low over low heat until frosting reaches 160°, about 8-10 minutes. Pour into the bowl of a heavy-duty stand mixer. Beat on high until frosting forms stiff peaks, about 7 minutes.
Spread over chilled pie. Just before serving, sprinkle with coconut. Store in the refrigerator.