Prepare canning jars according to manufacturer's directions. Pour cider and tequila into a large, heavy saucepan. Place 2 tablespoons of the sugar in a small bowl. Stir in the Sure-Jell® Light, mixing well. Add the Sure-Jell® Light mixture and the butter to the cider. Bring the liquid to a full rolling boil over high heat, stirring constantly. Quickly stir in the remaining sugar, and bring the mixture back to a full rolling boil again, continuing to stir. Boil 1 minute.
Remove pan from the heat. Skim off any foam. Fill prepared jars to within 1/8 inch of their tops. Process them in a water bath according to the manufacturer's directions, at least 10 minutes. The jelly may take several hours to set.
