Use a vegetable peeler, pressing firmly, to remove the orange zest in wide strips about 1½ to 2 inches long. Cut into very thin strips, about 1/8 inch wide.

Put the citrus zest in a small saucepan and fill with water. Bring to a boil and boil 5 minutes; drain. Repeat. Return the zest to the saucepan with the sugar and 2/3 cup water and bring to a simmer, stirring until the sugar dissolves. Cover and simmer for about 5 minutes, or until the zest is translucent and tender.

Transfer the zest and syrup to a small bowl. Cover and refrigerate overnight. (The zest can be refrigerated for several weeks.)

Using a slotted spoon, transfer the citrus zest to paper towels to drain before using. Sprinkle with additional sugar, if desired.