Cut guavas in fourths but do not peel.
Place in a small stainless steel or dutch oven with about 2 T. of water. Cook for about 10 minutes on medium heat, stirring to heat all of the guavas and they become mushy.
Turn off the heat and spoon the guavas into a fine mesh strainer over a clean bowl and using a rubber spatula push the pulp and juice leaving only the seeds and peels.
Return the contents of the bowl to the now cleaned dutch oven and add sugar and lemon juice.
Return to heat to a boil for about 10 minutes. The natural pectin in the guavas will start to thicken the mixture. Cook to gel point. (If your batch seems thin you can add 3 T. Flex Batch Pectin from Ball. )
Ladle mixture into 2 half pints and process in a water bath for 10 minutes at a full boil.