Make the Chickpea-Walnut Taco Crumbles according to the recipe you have 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, rinse briefly with cool water to stop cooking, and drain very well.
While the pasta cooks, finely dice the onion and mince the garlic.
Heat an extra-large skillet over medium-high heat and sauté the diced onion for 6–7 minutes, using 2–3 Tbsp water or vegetable broth for a no-oil method and adding a splash more if needed, until softened.
Add the minced garlic to the skillet and sauté 1–2 minutes until fragrant, 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 a creamy tomato sauce.
Add the creamy tomato sauce, diced tomatoes with their juices, and tomato paste to the skillet; stir to combine and gently simmer for 5–7 minutes to meld flavors.
Add the drained pasta and the prepared chickpea-walnut taco crumbles to the skillet; toss well with tongs until everything is evenly coated and heated through.
Turn off the heat and stir in 2–3 Tbsp fresh cilantro if using; serve with any desired optional toppings such as vegan cheese shreds, olives, red pepper flakes, pickled jalapeño, or vegan sour cream.
