Place cored cabbage head in an extra-large pot and cover with water. Bring the water to a boil on the stove. Once boiling, cover and cook for 5 to 7 minutes, rotating the cabbage occasionally with tongs or a large heat-resistant spoon, until the leaves soften, loosen, and begin to fall off the head. Remove the pot from heat. Carefully remove the cabbage head and leaves from the pot, drain it, and let it cool. Meanwhile, prepare the sauce and filling.
To make the filling: Combine onion, garlic, turkey, ketchup, tomato paste, and sugar in a large bowl. Knead with your hands until the mixture is evenly combined. Set aside.
To make the sauce: Combine cranberry sauce, jam or preserves, marinara sauce, and salt in a large glass measuring cup, and stir with a whisk or fork until smooth. Set aside.
Once the cabbage is cool enough to handle, gently remove 14 large leaves. (Refrigerate the rest for another use.)
Prepare the (empty) extra-large pot used to boil the cabbage by spraying it lightly with nonstick spray. Lay one cabbage leaf on a dry surface and spoon 2 heaping tablespoons of filling into the center of it. Spread filling out slightly and roll the cabbage up around the filling like a burrito, folding the sides in first and then rolling it up from the bottom.
Place it seam-side down in the pot. Repeat with remaining 13 leaves and remaining filling, gently stacking the rolls in the pot, if needed. Pour the sauce over the cabbage rolls, covering as much of the exposed cabbage as possible.
Cover the pot and set the stove temperature to low heat. Cook for about 1 hour, until the filling is cooked through.
Gently remove the cabbage rolls and serve topped with the sauce. Garnish with scallions, if you like!