In a large pot place the yuca, salt and enough water to cover. Bring to a boil, then reduce the heat to medium and cook for about 15 minutes or until fork tender.
Drain the yuca and remove any fiber from the center. Using a potato masher, mash the yuca, cover and set aside.
To prepare the meat filling: In a large skillet, heat the oil over medium-high heat. Add the onions, red bell pepper and cook until soft, about 3 minutes. Add the garlic, scallions, cumin, salt, black pepper and cook for about 1 minute, stirring often.
Add the ground beef and cook until the meat is cooked trough, about 7 minutes. Add the tomato paste and cook for 2 minutes more.
Remove from the heat, adjust the seasoning and let it cool.
To make the carimañolas: Divide the yuca mixture into 10 balls. Make a hole through the center of each ball with your finger. Place about 1 tablespoon of meat or cheese filling and gently close the ball, giving an oval shape.
In a large pot heat the vegetable oil and heat to 350° F. Add the carimañolas to hot oil and cook about 2 to 3 minutes until golden brown, turning them often.
Remove from the oil with a slotted spoon and drain on paper towels. Serve warm with ají.