Step 1 In a deep, heavy saucepan, bring the sugar, water and lime juice to a boil and continue cooking until the sugar darkens to a light brown color.
Step 2 In a separate saucepan, bring the cream and butter to a simmer. Remove from heat and keep in a warm place until the sugar is ready.
Step 3Very carefully whisk the cream and butter mixture into the sugar (the cream will steam and bubble as it is added). Continue whisking until the caramel sauce is smooth. Remove from heat and hold in a warm place. The sauce can be made ahead of time and refrigerated until needed; rewarm before using. This makes about 1 1/2 cups sauce.