Step 1Combine the sugar and water until it's the consistency of wet sand. Cook the mixture over high heat to a light golden caramel, about 10 minutes.
Step 2Add half the nectarines. Stir the fruit in a figure-eight pattern with a wooden spoon, keeping the heat as high as possible without splattering juice on your arm. It is important to stir quickly. This will prevent splattering and, most important, the fruit will maintain a fresh flavor, not a cooked caramelized taste.
Step 3Cook to a jammy consistency, about 7 minutes. Stir the remaining nectarines into the warm jam.