Preheat your oven to 450 degrees, line a baking sheet with tin foil, and set aside.
Scrub your potatoes, peel them, and slice into thin strips.
In a large microwave safe bowl, melt the butter in the microwave.
Add in the garlic, salt, chili powder, and pepper to the melted butter. Whisk together.
Toss the sweet potatoes into the melted butter mixture then spread onto the prepared baking sheet in a single layer. Spread them out so they're not overlapping, if possible.
Bake for 10 minutes, remove from oven, use a spatula to flip the fries, then bake another 10 minutes.
Remove from oven, sprinkle with more salt (if you think they'll need it), let rest on the pan for five minutes, then serve.