For the plum puree:
1lb fresh plums, pitted and quartered
¼ cup (50g) sugar or more to taste
For the ice cream base:
1½ cups (355 ml) heavy cream
½ cup (100g) granulated sugar
¼ cup mild flavored honey
¼ teaspoon kosher salt
1 cup (237 ml) buttermilk
¼ cup lemon juice, from Meyer lemons if available
Place the chopped plums in a saucepan along with the sugar. Cook until tender. Puree with an immersion blender or blender. Allow to cool completely.
Place half of the cream in a medium saucepan, Add the sugar, honey and salt and heat gently over a medium heat just until the sugar and honey dissolve. Do not let the mixture get too hot or boil.
Remove from the heat and place in a bowl. Add the remaining cream, buttermilk and lemon juice. Stir in the plum puree.
Set the bowl into a larger bowl of ice and water, and stir occasionally until the mixture is cool, taking care not to slosh water into the bowl. Remove from the ice bath, cover and refrigerate until very cold, at least 2 hours.
Churn in an ice cream maker according to the manufacturer's instructions. Place in a container in the freezer and freeze until hard.