Add olive oil to an oven safe skillet over medium high heat until just smoking. Add sausage and onions and cook until lightly browned, about 4 minutes. Add garlic and cook until fragrant, about 30 seconds.

Add broth, tomatoes, cream, pasta, salt and pepper.

Stir and bring to a boil, cover skillet, and reduce heat to medium-low. Simmer until pasta is tender, about 15 minutes.

Remove skillet from beat and stir in 1/2 cup cheese. Top with remaining cheese and sprinkle scallions. Broil in oven until cheese is melted, spotty brown, and bubbly.