Make the raspberry swirl: In a small saucepan, combine raspberries, sugar, and lemon juice. Cook over medium heat, stirring and mashing until saucy (about 3-4 minutes). Let cool, then press through a sieve for a smoother sauce (optional).

Whip the cream: In a chilled bowl, whip the heavy cream, powdered sugar, and vanilla until soft peaks form.

Layer it up: In 4 small glasses, dollop in whipped cream and drizzle raspberry sauce in layers. Gently swirl with a skewer or spoon handle for a marbled look.

Chill (or not!): Serve immediately, or refrigerate up to 2 hours for a colder, slightly thicker treat.