Combine butter, flour and sugar;mix until crumbly. Press in bottom of 9x13-inch pan. Bake at 350 degrees for 10 minutes. Set aside.
Combine 2 cups sugar, flour and salt;gradually stir in cream. Beat egg yolks until very light. Blend into sugar mixture. Add rhubarb. Spoon over warm shortbread crust. Bake at 350 degrees for 60 minutes. Beat egg whites until they form soft peaks. Add remaining 3/4 cupsugar, gradually, beating until stiff and sugar is dissolved. Stir in vanilla. Spread over rhubarb layer, starting at edges and working toward center. Carefully seal meringue to outer edges of pan. Continue baking for 15 minutes or until golden. Serves 16 to 18 with icecream. (Dorothy Dean, May 1976)