Place the heavy cream and sugar together in a saucepan. Bring to a boil over medium/high heat, whisking to dissolve the sugar. Reduce heat to medium and summer for 5 minutes. Watch closely as the cream boils - keep the heat low enough that it does not boil over.
Remove the pan from the heat and whisk in the lemon juice.
Let sit for 15 minutes, giving a whisk every few minutes - mixture will thicken as it sits.
Divide the cream mixture between 4 ramekins.
Refrigerate for 2 hours or until set.
Top with fresh fruit (or roasted rhubarb, as I did here).
Recipe by The Kitchen McCabe at https://www.thekitchenmccabe.com/2020/08/02/lemon-possets/