Warm olive oil in a large skillet over medium heat. Add the spinach with a pinch of salt, and cook, stirring occasionally, until wilted (about 3 minutes). Let spinach cool, then place on two layers of paper towels. Bring the corners of the paper towels up around the spinach and squeeze out as much liquid as you can over the sink.
Cover with foil and bake for 30 minutes. Remove the foil, then bake until the cheese is melty and golden on top (about 15 minutes more). Let cool for 10 minutes before serving.