In a medium bowl, combine the heavy cream and buttermilk. Stir well to mix.

Cover the bowl with a clean kitchen towel or plastic wrap and let it sit at room temperature for 12 to 24 hours until thickened.

Once thickened, stir in the lime juice and salt until well combined.

Transfer the crema to a jar with a lid and refrigerate. Use as desired on tacos, enchiladas, or other dishes.