Start by rinsing the ripe plums under cool water, then pit and quarter them. Place the quartered plums into a medium-sized saucepan.

In the same saucepan, add granulated sugar, water, ground cardamom, and a pinch of salt to the plums. Stir gently to mix.

Place the saucepan on the stovetop over medium heat, allowing the mixture to come to a gentle simmer. Stir occasionally for 10 to 15 minutes, or until the plums soften.

Once the plums are softened and the sugar is dissolved, remove the saucepan from heat and allow it to cool slightly for about 10 minutes.

After the mixture has cooled, transfer it to a blender. Blend on high speed until smooth.

Using a fine-mesh sieve, strain the blended puree into a bowl, discarding any solids that remain.

Stir in the freshly squeezed lemon juice into the strained puree, mixing well.

Cover the bowl containing the mixture with plastic wrap or a lid, and refrigerate it for at least 2 hours.

Once chilled, pour the mixture into an ice cream maker and churn according to the manufacturer's instructions for 20 to 25 minutes.

To achieve a firmer sorbet, transfer the churned sorbet into a container and cover it tightly. Freeze for an additional 2 to 3 hours.

Once frozen to your desired firmness, scoop the sorbet into chilled bowls or dessert glasses and serve immediately.