In a heatproof saucepan, combine the sugar, corn syrup, water, and lemon juice. Heat over medium until the mixture reaches 250°F (firm-ball stage) using a candy thermometer.

Remove from the heat and stir in melted butter, fruit extract, and food coloring if desired.

Mix together the gluten-free flour, cornstarch, salt, and xanthan gum in a bowl, then add it to the sugar mixture. Stir until a thick, pliable dough forms.

Allow the dough to cool slightly, then divide and roll into long rope shapes on a parchment-lined surface.

In a small bowl, combine powdered sugar with citric acid. Roll each rope in the mixture until evenly coated.

Leave the candy ropes to firm up at room temperature for 1 to 2 hours before enjoying or storing.