Remove the cake from the oven, let it sit in the pan for about 10 minutes, then turn it out onto a wire rack. Prick the hot cake several times with a wooden skewer.
Immediately prepare the caramel: In a large heavy skillet, melt the sugar over medium-high heat, without stirring. (As the sugar begins to melt, shake the pan occasionally so that the caramel turns an even golden brown. You don’t want the caramel to get too dark or it will taste bitter.) Add the nuts and cream and stir with a wooden spoon until the caramel is dissolved again. Spread the caramel over the hot cake, poking it again several times so that it runs into the holes.
Let the cake cool.