Saute green onions with olive oil in a large skillet over medium heat for 2 minutes.
Add fennel sliced very thin and cherry tomatoes. Season with salt and pepper. Increase the heat and cook until the tomatoes are slightly blistered and the fennel is thoroughly cooked.
Stir in spinach until cook until wilted. Meanwhile, cook pasta according to package directions. Drain reserving a little of the pasta cooking water.
Combine pasta with sauce mixture in the skillet. Add reserved cooking water and cook until the liquid is completely reduced. STIR in cheese and fennel tops before serving.
