To prepare the caramel sauce, combine sugar and water in a heavy saucepan set over low heat, cook until the sugar is dissolved. Add the butter. Let it come to a boil and cook until it reaches a golden caramel color.
Remove from the heat and add the cream slowly. Be careful as it will splatter. Whisk to combine. Add salt to taste. Let cool slightly.
Preheat oven to 350F. Grease the bottom and sides of an 8-inch cake pan. Line the bottom with parchment paper. Set aside.
Sift flour, baking powder, baking soda and salt in a large bowl.
In another bowl, mix eggs and sugar until well combined. Gradually add oil and vanilla, mix until just blended.
Slowly add half the flour mixture; mix until just blended. Add the buttermilk, mix until just blended. Add remaining flour mixture, mix until batter is combined and smooth.
Pour the batter into the prepared pan and smooth the top.
Bake 18 to 20 minutes or until a toothpick inserted in the cake comes out clean.
Remove the cake from the oven and let cool completely.
To prepare caramel cream filling, mix cream cheese and half cup of caramel sauce in a food processor until combined.
Whip the heavy cream until it holds soft peaks. Add the cream to the cream cheese mixture and fold with a spatula until it becomes one liquid.
To assemble, line the bottom and sides of an 8-inch springform pan with parchment paper.
Place in the vanilla cake layer. Then pour the caramel cream mixture over the cake. Juggle to lightly level the top. Chill in the refrigerator for at least 4 hours.
Remove cake from the refrigerator. Transfer cake from cake pan to a serving plate. Peel off the parchment papers. Top the cake with more caramel sauce and nuts, if desired.