Wash the tripe, and drop into a pot of boiling water for 45 minutes. Drain, cool, and cut into pieces each about 2 inches wide. Cut each piece into ½-inch strips, and set aside.
Heat the olive oil, add the onion and cook until translucent but not browned. Add the tomato puree together with the oregano, salt, and pepper. Bring the sauce to the boil, add the tripe, lower the heat, cover,