Seed and roughly chop a jalapeno. Discard the seeds and the stem.
Add 1 cup mayonnaise, the chopped jalapeno, and lime juice to a blender or food processor and pulse until the jalapeno is sliced into tiny pieces. If you do not have a blender, you can finely mince the jalapeno and mix it with the mayo and lime juice to combine.
Store in a sealed container in the refrigerator for up to a week.