Beat egg yolks in a medium mixing bowl until thick and lemon colored. Add milk and lime juice; blend well. Spoon filling into graham cracker piecrust.
Combine egg whites (at room temperature) and cream of tartar; beat until foamy. Gradually add sugar, 1 tablespoon at a time, beating until stiff peaks form. Spread meringue over filling, sealing to edge of piecrust. Bake at 350° for 10 minutes or until meringue is golden brown. Cool to room temperature. Chill.