Heat the olive oil in a large skillet or sauté pan over medium high heat. Add the onion and zucchini. Cook, stirring often, for 5 minutes, or until the onion is clear and the zucchini is soft and cooked through.
While the vegetables cook, crumble the tofu with your hands, so that there are still some visible pieces, but it's broken up quite thoroughly. If you're using frozen spinach, add it to the tofu now.
When the zucchini is ready, add the tofu and spinach to the skillet, along with the tahini, nutritional yeast, turmeric, and a couple tablespoons water. If you're using fresh spinach, add it now. Mix everything well, and heat it for a few minutes, till it's warmed through and the spinach is fully cooked. Season the mixture to taste with salt and pepper. Serve.