Wash the ripe plums thoroughly, pit and slice them into quarters, and place them in a medium saucepan.

Add granulated sugar, water, ground cardamom, and a pinch of salt to the saucepan with the plums, stirring well.

Heat the saucepan over medium heat and bring to a gentle simmer for about 10-15 minutes, until plums soften and sugar dissolves.

Remove from heat, allow to cool slightly for about 5 minutes, and blend until smooth.

Strain the blended puree through a fine-mesh sieve into a bowl to remove solids and skins.

Stir in fresh lemon juice, cover with plastic wrap, and refrigerate for at least 2 hours.

Pour the mixture into an ice cream maker and churn according to the manufacturer's instructions.

Transfer to an airtight container and freeze for an additional 2-3 hours for a firmer texture.

Serve scoops in chilled bowls, garnished with fresh mint leaves or whipped cream if desired.