Return the peels to the saucepan. Add the remaining 2 cups water, 1 1/2 cups of the granulated sugar, and 1/2 teaspoon kosher salt. Stir to combine and bring to a simmer over high heat. Reduce the heat to medium low and simmer until the peels are translucent and the syrup is thickened, 20 to 25 minutes. Meanwhile, line a baking sheet with parchment paper and place a wire rack on top.
