When making a pie filling that contains gelatin, you need to cool the mixture first until it is partially set before pouring it into the shell. To do this, you can either place the filling in the refrigerator for about an hour and stir occasionally, or cool the mixture in the pan directly over a bowl of ice water, which takes only about 15 minutes.
Cooling Gelatin over Ice Bath
In a saucepan, stir together the gelatin and cherry juice. Let sit 5 minutes to soften the gelatin. Cook over low heat, stirring, until the gelatin dissolves. Remove from heat and set the saucepan in a large bowl of ice water.
Checking Gelatin Consistency
As the gelatin chills, it will begin to thicken. Stir often until the mixture is partially set (it will have the consistency of unbeaten egg whites). This should take about 15 minutes. Add more ice to bowl, if necessary, to maintain a cold temperature.