Cut each potato in half lengthwise, then cut each half into about six long wedges.
Alternatively, cut each potato into thin rounds. A mandoline (a hand-operated device
that evenly slices vegetables) also can be used to cut uniform wedges or rounds.
Transfer the cut potatoes to a large zip-lock plastic bag. Add the oil, cumin
and chili powder. Seal the bag and shake to evenly coat the potatoes.
Transfer the potatoes to a baking sheet and arrange in a single layer.
Bake for 50 minutes, or until the fries are crisp. For more even crisping, use
a spatula to flip the fries after 25 minutes.