Cook the rhubarb, sugar, lemon juice, rosewater, and peppercorn in a medium-sized heavy saucepan set over medium heat until the fruit softens and most of the liquid cooks out but the fruit is not sticking to the bottom of the saucepan, about 12 to 14 minutes, stirring frequently.
Whip the cream for a minute, adding the sugar when it thickens up a bit. Beat until soft peaks form. Fold in the crème fraiche, briefly beating it in until smooth soft peaks form, lustrous, and thick.
Spoon a 1/4 cup dollop of whipped crème fraiche into six tumbler glasses. Stir in a tablespoon of rhubarb compote into the cream with a chopstick, swirling it in slightly, but only enough so there’s a marbled ribbon of fruit lacing through the cream. Top each tumbler with another 1/4 cup dollop of cream, and top each tumbler with a teaspoon of the remaining compote. Chill for 10 minutes or eat.