Prick 4 sweet potatoes with a fork. Place on a baking sheet and bake at 400 degrees F until soft, 60 to 75 minutes. Mix 6 tablespoons softened butter, 1 tablespoon chopped dill, 1 small sliced scallion and 1 1/2 teaspoons grated lemon zest; season with salt and pepper. Cut open the potatoes and top with the dill butter.