Bring 6 quarts water to boil and add 2 tablespoons salt.
In a mixing bowl, stir together crab, scallions and basic tomato sauce until well blended. Cut pasta into 4-inch squares and place 1 tablespoon filling in center. Fold into triangles, exude air and seal edges. Bring points of long side together to form a ring (or a hat!!) and seal with pressure between fingers. Place tortelloni in water and boil for 8 to 10 minutes. Meanwhile, melt butter with poppy seeds. Drain cooked tortelloni carefully and gently place in pan. Add remaining scallions and toss to coat. Serve immediately.