Cut the lemon and plum as directed above. Place them in a bowl with the sugar. Stir to incorporate and set aside for 20 minutes.
Remove the fruit from the bowl and squeeze excess juice into the bowl. A syrup will be left in the bottom of the bowl. Stir slightly to help dissolve the remaining sugar granules.
Divide the syrup between to highball glasses.
Pour the whiskey evenly between the two glasses after the syrup.
Place ice in each glass.
Fill each glass with 7up, pouring it directly over the ice.
The syrup will remain at the bottom for serving but we recommend stirring it together before drinking.
Enjoy!!!
Recipe by Meatless Makeovers at https://www.meatlessmakeovers.com/preserved-lemon-plum-highball/