In a medium bowl, mix the sour cream with the dulce de leche until combined.
Adjust the oven rack to the lower third of the oven and preheat to 350°F.
Remove the springform pan from the refrigerator. Gently spread the cream cheese filling evenly, trying not to distress the crust. Place the cheesecake in the oven and bake for 35 minutes, or until it is set and the top is lightly browned. Remove from the oven and let cool for at least 10 minutes before you add the dulce de leche topping.
Spoon the dulce de leche topping over the cream cheese filling, add the pecans all around the edge and place the pan back in the oven for 10 more minutes. Remove from the oven and let the cheesecake cool to room temperature. Cover and refrigerate for at least 4 hours before serving. It tastes even better if it chills overnight.
Before serving, run the tip of a wet knife around the edge of the pan to release the cheesecake. Remove the ring, then slice and serve the cake.