Step 1

Tear out flesh from orange halves, being careful not to create any holes in peels. It’s okay if you can’t remove all of the pith. Save flesh for another use; cut peels into ¼" strips.

Step 2

Bring orange peels and 4 cups water to a boil in a large saucepan and cook 5 minutes. Drain and return peels to pan. Repeat process twice more, using fresh water each time. Return peels to pan; add 2 cups sugar and 2 cups water. Bring to a boil and cook until peels are soft and translucent and vibrant looking, 30–40 minutes (about 10 minutes longer for grapefruit, or 10 minutes less for lemons or limes). Drain and transfer peels to a wire rack set inside a rimmed baking sheet; chill until cool, about 15 minutes.

Step 3

Whisk citric acid and remaining 1 cup sugar in a medium bowl. Add peels; toss to coat. Return to rack; let sit at room temperature 1 hour. Toss peels again in sugar mixture. Return to rack; let sit 4–12 hours to dry out.

Step 4

Do Ahead: Citrus peels can be candied 1 month ahead. Store airtight at room temperature.