In a deep saucepan over medium-high heat, cook the brown sugar, cream, corn syrup, and salt for 2 minutes without stirring. The caramel will start to bubble rapidly. Then swirl the pan gently to stir the caramel (instead of using a spoon), continuing to cook until the bubbles get larger and slower, 1 to 2 minutes. Turn off the heat and add the lime juice. Stir with a rubber spatula to combine.
Transfer the caramel to a small bowl and let it cool to room temperature. Or cover the bowl and store it in the refrigerator for up to 1 week (let it soften to room temperature before using it).
Recipe by Susan Feniger. Reprinted with permission from Susan Feniger's Street Food, Clarkson Potter, 2012.