Chop your plums roughly and add them to a medium sized saucepan.
Add the sugar & lemon juice, and give the mixture a quick stir.
Place the saucepan over medium heat.
While stirring occasionally, bring the fruit mixture to a boil.
Boil for about 10 minutes, while stirring periodically, until soft and jammy.
Once cooked, remove from the heat. Using a potato masher, mash the remaining fruit pieces.
Next, take a fine mesh sieve and place over a a medium sized mixing bowl. Pour the cooked fruit into the sieve. Using a rubber spatula, scrape the fruit through the sieve, releasing the juices and keeping the pulp.
Discard the pulp (or eat over yogurt, like I like to do!).
Let the reduction cool, and place into an airtight storage container. Refrigerate.
Use within 3-5 days.