Step 1Pit the plums: Most varieties are not freestone; working on a cutting mat, cut the plums in half vertically, shaving alongside the pit. Cut away the remaining meat clinging to the pits and coarsely chop the plums. If very ripe, the plums may fall apart. Scrape the plums and their juices into a medium nonreactive bowl. Stir in the sugar, ginger, garlic and fresh chile, seeded and chopped. Macerate 1 hour.
Step 2Using an immersion blender and beaker or a small food processor, puree the plum mixture with ½ teaspoon salt and the aji amarillo salsa to the consistency of heavy cream. Taste the salsa; it should be sweet, hot and tart. Add salt, lime and salsa to taste. The salsa may be held at room temperature for several hours, and covered and refrigerated up to 1 week.