Remove the seeds from pomegranates. Pass the seeds through a food mill fitted with the large-holed plate.
Strain the juice through a fine-mesh strainer or cheesecloth. Press the pulp with the back of a wooden spoon or squeeze the cheesecloth to extract all the juice. Measure and set aside 1 1/2 cups juice.
Measure 1/4 cup water into a small metal or heat-proof bowl. Sprinkle gelatin over the top of the water in an even layer. Set aside to let the gelatin "bloom".
Measure 1 1/2 cups water and sugar into a small pot. Bring to a boil, stirring to dissolve the sugar. Remove from the heat.
Set the bowl of bloomed gelatin on top of the pot of sugar water to melt gelatin.
Once the gelatin is melted, stir it into the pomegranate juice. Pour in the warm sugar water and stir again to combine.
Taste the mixture. Add if desired: a squeeze of lemon juice, and a splash of rosé wine.
Pour the mixture into an 8-inch square baking dish and put in the refrigerator. (Make sure you have a flat surface in the refrigerator to set the dish on.) Let the mixture jell completely before serving. Once it has set, cover tightly with plastic wrap. Gelée will keep for up to 3 days in the refrigerator.
To serve, drag a knife though the gelée lengthwise and crosswise to cut it into cubes and spoon them into small bowls. Garnish with slices of peach, nectarine, strawberries, or other fruit.