Measure heavy cream into a large mixing bowl. Briskly stir in the fresh lime juice, and grate in the lime zest. The acidity of the lime will thicken the cream naturally
Italian Meringue Frosting
Measure sugar into a saucepan and add water until it is just covered. Heat the sugar water on low and stir gently until the sugar dissolves into the liquid.
Turn up the heat to medium and bring the mixture to a boil. Place the sugar thermometer into the sugar syrup and wait until it reaches 115 degrees Celsius / 240 degrees Fahrenheit.
Whip egg whites with an electric hand whisk or mixer until stiff peaks form. Slowly add the sugar syrup whilst continuing to whisk once it hits 120 degrees Celsius / 250 degrees Fahrenheit