Preheat oven to 450°. Bring a large pot of water to a boil. Trim ends of yuca and cut each one in half, widthwise. Stand them on their ends and use a sharp knife to cut the waxy peel off. Cut each piece in half lengthwise and then cut in half lengthwise one more time to create 16 pieces total. Trim the fibrous center out of each piece.

Place cut yuca into boiling water and let boil until fork tender, 8 to 10 minutes. Using a slotted spoon, remove from pot and place on a paper towel lined cutting board. Pat dry with another paper towel.

Place dried yuca into a large bowl and toss with oil. Season with chili powder, salt, and pepper and toss again to evenly coat. Place yuca on a large baking sheet in an even layer.

Bake until golden and crispy, about 25 minutes, tossing halfway through.

Meanwhile make dipping sauce: In a small food processor or blender, combine avocado, sour cream, lime juice, and cilantro and blend until smooth. Season with salt and pepper.

Serve fries immediately with dipping sauce.