Bring a large pot of salted water to a boil. Peel cassava, chop in half and slice horizontally. Place in boiling water and boil until tender. Remove and reserve.
Put oil in a pan along with diced onion and garlic. Cook in the pan until onions are cooked. Monitor the heat. You want to infuse the oil with flavor, not burn the ingredients. If you want it spicier, you can add the pepper at this stage.
Pour the hot oil directly over the cassava. Zest a lime and sprinkle it on top. Squeeze the juice of the lime on top. Add red pepper flakes and garnish with scallions.
