Rinse fresh raspberries or thaw frozen raspberries, mash with a potato masher in single layers until fully crushed. Measure mashed berries to have 5 full cups.
For the lime zest, use two different sized zester tools, if available. Use a fine zester to get the lime essence, and one a bit larger so that you can see some flakes of green here and there. Juice two limes to make 4 tablespoons of juice, for a really bright flavor.
Mix berries, lime zest and juice together in a 6-8 quart saucepan over medium heat. Mix until fully combined. Gradually add powdered pectin. Bring mixture to a full rolling boil over med-high heat, that doesn’t stop boiling when stirred. Add full measure of sugar, stirring to dissolve. Return mixture to full rolling boil and boil hard for one minute, stirring constantly.
Remove from heat, stir and skim any foam off of top.
Pour jam into hot, sterilized jars, clear jar rims and thread tops of any jam residue with a clean, damp cloth. Apply lids to jars, then apply bands and adjust until fit is fingertip tight. Process in a water bath canner for 10 minutes following home canning instructions from a recognized source such as the National Center for Home Food Preservation.