Caramelize the sugar and finish the sauce (see the Note on cooking caramel successfully):

In a heavy-bottomed saucepan combine the sugar, ¼ cup water, and the cream of tartar. Cover and cook over high heat until it comes to a very rapid boil. Remove the cover and continue to cook at medium-high heat until the sugar takes on a golden brown caramel color. Remove from the heat, stand back, and slowly add the cream. The mixture will bubble and steam furiously. When the bubbling has subsided, return to the heat. Whisk the caramel and then let the mixture come to a rolling boil. Immediately remove from the heat and add the rum.

Serving Suggestions:

This sauce should always be served warm. To reheat this sauce after it has been refrigerated, either heat the sauce directly over the stove, stirring with a rubber spatula, or place the container of sauce in a bowl of hot water. It goes well with any chocolate dessert, and with the Maple Walnut Souffle, Pumpkin Souffle, and Roasted Apple Beignets.