Cut the lemons in half and use a spoon to scoop out the insides as much as you can. Place halves into a muffin tin to keep them upright. Heat 1 cup of juice in a pan over medium heat and stir in packets of gelatin slowly until dissolved. Combine with the other cup of cold juice in a pourable container and once mixed, pour the liquid into lemon halves until each is half full. Refrigerate for 4 hours or until set. Once set, remove the tins and slice lemon halves into thirds right before serving. *Tip: To make an alcoholic version, swap out 1 cup of juice with your favorite vodka or rum.