Soften the butter at room temperature.
Finely chop the jalapeño, removing the seeds for a milder flavor if desired.
In a mixing bowl, combine butter, jalapeño, minced garlic, lime juice, chopped cilantro, black pepper, and salt.
Mix thoroughly until all ingredients are evenly incorporated.
Shape into a log using parchment paper or transfer to an airtight container.
Refrigerate for at least 1 hour until firm.
Slice or melt over grilled meats, corn, vegetables, potatoes, burgers, or bread.