Place raspberries, cream, sugar, lemon zest, and salt in a heavy-bottomed saucepan over medium heat. Bring to a gentle boil, stirring frequently.
Reduce heat to medium-low and cook for 8 minutes, stirring constantly.
Pour mixture into a fine mesh sieve set over a bowl. Use the back of a spoon or spatula to press on the mixture and extract as much of the liquid as possible. Discard solids.
Add lemon juice to the strained raspberry cream mixture, and whisk until mixture begins to slightly thicken, 30 to 60 seconds.
Pour mixture evenly into ramekins. Chill ramekins in the refrigerator for at least 4 hours.
Serve possets cold, garnished with a few extra raspberries, if desired. Store in the refrigerator.
