Preheat the oven to 350 degrees F. Coat a 9" square pan or 2 quart casserole dish with cooking spray.
Place the sweet potatoes, granulated sugar, salt, vanilla extract, eggs and 6 tablespoons of butter in a mixing bowl.
Beat with a mixer until well blended and fluffy.
Spoon the sweet potato mixture into the prepared dish in an even layer.
In a medium bowl, mix together the remaining 6 tablespoons of butter, brown sugar, flour and pecans.
Sprinkle the brown sugar mixture over the sweet potatoes.
Bake for 30-40 minutes or until sweet potatoes are hot and topping is lightly browned. If your topping browns too quickly, you can cover your dish with foil to complete the bake time.
Let sit for 10 minutes, then serve.