Preheat the oven to 400 degrees F. Grease a baking sheet with non-stick cooking spray.
Peel the sweet potatoes. Grate them using the large holes of a box grater or a food processor fitted with the grating disc. Gently squeeze the shredded potatoes with a towel to remove excess moisture.
Combine the potatoes, cumin, chili powder, garlic powder, onion powder, kosher salt, black pepper, flour and scallions in a large bowl.
Stir in the egg.
Portion out the fritter batter by the 1/4-cup-full. Form them into patties, but do not pack them too tight. They should just be able to hold their shape. Space them 2-3 inches apart on the pan.
Bake the fritters for 25-30 minutes until they are browned on both sides, flipping them over just over halfway through baking.
Garnish them with chopped parsley and serve with sour cream if wanted.