Preheat the oven to 450 degrees.
Melt the butter and skim off the foam. Add garlic, seasoned salt, chili powder, and black pepper. Stir with a fork.
In a large bowl, toss the sweet potatoes in the butter/seasoning mixture. Arrange on two baking sheets and bake in the oven for 15 to 17 minutes, shaking the pans halfway through, until the fries are sizzling (watch so that the edges don't burn). Remove from the oven and allow to sit on the pan for 5 minutes. Sprinkle generously with salt!
Mix the mayonnaise with the ketchup (or Sriracha). Serve fries with the dipping sauce!