In a microwave, defrost the spinach, then wring dry in a clean kitchen towel. Bring a large pot of water to a boil, salt it, add the pasta and cook until al dente. Drain and return the noodles to the pot.
While the pasta is working, in a medium skillet, heat the EVOO, 1 turn of the pan, over medium heat. Add the onion and garlic, and cook until tender, 8-10 minutes. Add the spinach, breaking it apart, to heat through. Season with salt and pepper. Remove the pan from the heat.