Making a caramel sauce: Pour 2 cups of the cream into a medium saucepan and slowly bring to a boil. Lower the heat and keep at a bare simmer.
Put 1 cup sugar in a heavy medium saucepan over medium heat. Leave undisturbed until the sugar begins to melt and darken. Gently shake the pan to distribute the sugar and to keep the melted sugar from burning. When all the sugar has melted and the caramel is a dark amber, remove from the heat. Carefully add the hot cream, stirring constantly with a wooden spoon. Don't worry if the caramel hardens; it will melt as the sauce boils. Return the pan to the heat and keep at a gentle boil for 5 minutes, stirring constantly. Set aside for at least 30 minutes, stirring often, until the sauce is cool. Measure 1 cup of the caramel to add to the cake batter and refrigerate the remaining caramel.
To make the cake: Preheat oven 325. Grease and flour a 12 cup Bundt pan.
Cream the butter and remaining sugar until fluffy. Add the eggs, one at a time, waiting until each has incorporated before adding the next egg.
Sift together the flour, baking powder and salt. Gently, but thoroughly fold the flour mixture into the butter mixture, alternating with the reserved cup of caramel, beginning and ending with the flour mixture.
Pour the batter into the prepared pan and bake until a skewer comes out clean, 35-40 minutes. Set the pan on a rack for about 10 minutes and then unmold and let the cake cool completely on the rack. Bring the rest of the caramel sauce to room temperature. When the cake is cool, drizzle half the remaining caramel sauce over the top.
Whip the remaining cream until it holds firm peaks. Gently fold in the remaining caramel, leaving streaks visible. Serve this dolloped on top of each cake slice.