In a medium saucepan, melt the butter over medium heat. Add the shallots and saute until they are soft, about 5 minutes. Add the stock, rice, wine and tomato paste, increase the heat to medium-high and bring to a simmer. Reduce the heat to medium-low and simmer for 25 minutes.
Stir two-thirds of the crab meat into the soup, then transfer it to a blender (work in batches if you have a small blender) and puree until smooth. Return the pureed soup to the saucepan and place over medium-low heat.
Stir in the remaining crab meat, cream, salt and cayenne pepper. Heat until the cream and crab meat are warmed through, about 5 minutes. Leftovers can be stored in the refrigerator for up to 2 days.