In a large bowl, combine the flour and sugar; cut in butter until mixture resembles coarse crumbs. Press mixture into an ungreased 8-in. square baking dish. Bake at 350° for 15-20 minutes or until lightly browned. meanwhile, in a small bowl, combine sugar, flour and salt. Beat in cream and egg yolks. Stir in rhubarb. Pour over hot crust. Bake, uncovered, for 40 minutes or until set.
In a bowl, beat egg whites and vanilla on medium speed until soft peaks form. Spread over hot filling, sealing edges to baking dish.
Bake for 15 minutes or until golden brown. Sprinkle with coconut. Cool on a wire rack. Cut into squares. Refrigerate leftovers. Yield: 9 servings.