1. Preheat oven to 375 degrees F.
2. Pierce sweet potatoes all over with a fork. Microwave on HIGH for 15 minutes or until completely cooked through. Let rest 5 minutes or until cool enough to handle.
3.Topping: Meanwhile, combine the pecans, flour, sugars, cinnamon and 1/4 tsp. salt. Stir to blend. Mix in 1/4 cup butter. The topping should form sandy clumps. Refrigerate.
4. Split the potatoes in half lengthwise and scoop out some of the flesh inside. Arrange the sweet potato "halves" on a baking sheet. In a medium bowl, combine the sweet potato flesh with the remaining 1/4 cup butter, orange zest and 1/2 tsp. salt. Spoon the filling back into each potato half and top with the topping on a baking tray. Place the tray in the center of the oven and bake until the topping browns, 15-20 minutes. Serve immediately.