Pour boiling water over the raspberry gelatin and stir until dissolved.
Add sugar and salt and chill mixture until thick and syrupy.
Turn the well-chilled cream (or evaporated milk) into a chilled bowl and whip until stiff; add lemon juice and continue beating until very stiff.
Using same beater, whip up gelatin until light and fluffy; then add the stiffly whipped cream and fold in thoroughly.
Turn into a 4-cup mold which has been rinsed with cold water.
Chill until firm.
Unmold onto a chilled serving plate.
Garnish by piping with whipped cream, if desired.
This same method may be used for any fruit-flavored gelatin.
A pleasing variation is to fold in the whipped cream only partially to give a marbled appearance.