Poke holes in sweet potato with a fork, and cover with a damp paper towel. Place on a microwavable dish, and microwave on HIGH until tender, about 7 minutes. Remove from microwave, and let stand at room temperature until cool enough to touch about 5 minutes.

Remove sweet potato flesh with a spoon, and place in a medium bowl. Discard sweet potato skin. Cool to room temperature, about 10 minutes. Add masa harina and salt, and stir until a dough forms and all masa harina is incorporated. 

Divide dough into 8 portions (about 1 1/4 ounces each). Roll into balls. Using a tortilla press lined with plastic wrap, press each ball into a 5-inch tortilla. Cook each tortilla in a nonstick skillet over medium until toasted on each side, about 60 seconds per side. Transfer to a plate, and use immediately or store in a plastic ziplock bag in the refrigerator up to 5 days.