Giadia's Braised Spinach

Ingredients
1/4 cup extra-virgin olive oil
2 large red onions, sliced
4 garlic cloves, minced
4 large bunches fresh spinach, washed with water still clinging to leaves, stems trimmed and leaves coarsely chopped
2 tablespoons soy sauce
3/4 teaspoon dried crushed red pepper flakes
Salt and freshly ground black pepper
Directions
Heat the oil in a very large pot over medium heat. Add the onion and garlic, and saute until tender, about 8 minutes. Add 1/3 of the spinach and saute until it begins to wilt, about 1 to 2 minutes. Continue adding the spinach 1 handful at a time, sauteing just until it begins to wilt before adding more. Add the soy sauce and crushed red pepper. Saute over high heat until spinach wilts. Season the mixture, to taste, with salt and black pepper. Transfer the mixture to a bowl and serve.