Prepare the Chickpea-Walnut Taco Crumbles according to the recipe you use and set aside.
Bring a large pot of salted water to a boil and cook the spaghetti until al dente according to package instructions; drain in a colander and rinse with cool water to stop cooking, then drain very well.
While the pasta cooks, finely dice the onion and mince the garlic.
Heat an extra-large skillet over medium-high. Add the diced onion and sauté 6–7 minutes using 1–3 tablespoons water or vegetable broth for a no-oil method, adding small splashes as needed until softened.
Add the minced garlic to the softened onion and cook 1–2 minutes, then reduce the heat to medium-low.
In a small bowl, whisk together the tomato sauce, dairy-free milk, nutritional yeast, and tamari to make the creamy tomato sauce.
Add the creamy tomato sauce, diced tomatoes with their juices, and tomato paste to the skillet; stir and gently simmer 5–7 minutes to meld flavors.
Add the drained spaghetti and the prepared Chickpea-Walnut Taco Crumbles to the skillet; toss with tongs until everything is evenly combined and heated through.
Turn off the heat and stir in 2–3 tablespoons chopped fresh cilantro if using. Serve immediately with desired optional toppings.