Heat vegetable oil in a large skillet over high heat until oil is hot; decrease heat to medium. Cook and stir onion and potatoes in the hot oil until potatoes are lightly browned and partially cooked, 15 to 20 minutes. Add squash, butter, paprika, black pepper, garlic powder, salt, and red pepper flakes; cook until potatoes are golden brown, 15 to 20 more minutes, turning occasionally. Remove from skillet with a slotted spoon.
