Preheat the oven to 400 degrees F.
Wash the sweet potatoes, scrubbing them well to remove any dirt. With a fork, prick the sweet potatoes in a couple of spots and place them on a rimmed sheet pan. Bake for about 45 minutes, or until a knife inserted in the center goes in easily.
IF YOU PREFER CREAMY SWEET POTATOES, INSTEAD OF SLICED, FOLLOW THE TIME SAVING TIP IN THE COMMENT ABOVE.
In a large bowl, mix the butter, brown sugar, and flour together until it's crumbly-looking. Add the cinnamon, salt, pecans, fold the streusel topping together to combine.
When the sweet potatoes cool off, remove the skin and slice them into 1" thick slices. Arrange them in greased 9 x 13 baking dish. Spread the streusel topping on top.
Bake for another 20 minutes, or until the topping is bubbly and brown.