To be extra safe, hold the dethorned fruit with a pair of tongs and cut them in half with a sharp knife, then cut off the end with the thorns. Scoop out the flesh with a spoon.
Place the water, sugar, and pear flesh in a medium saucepan. Bring to a gentle boil, then reduce heat to medium-low and simmer for 30 minutes.
Remove from heat and set aside to cool.
Carefully pour the syrup mixture into a blender or food processor, and blend until smooth.
Pour the mixture into a large measuring cup through a fine mesh sieve, or strainer, to remove the seeds.
Stir in the lime juice and pour into a sealable bottle or air-tight container. Store in the refrigerator until ready to use.
Notes
Fresh cactus fruit is good for one week after picking.
Prickly pear simple syrup will last in the refrigerator for about a week, or in the freezer for up to one year.
The juice from the prickly pear fruit WILL STAIN everything it comes in contact with. It washed off my white countertop and wore off my fingernails in 24 hours. Wear gloves if you are concerned.