Spiralize the zucchini into long pasta like noodles. Set aside until needed.
Combine the broth and saffron in a small pot. Put the pot on the stove and turn up the heat to high. Bring to a boil and cook until the liquid reduces to 1 cup, approx 10 minutes. Turn off the heat.
While the saffron sauce is working, cook the pasta according to your favorite method (or manufacturers instructions), drain, and set aside until needed. I undercook my pasta by 2 minutes, knowing it will cook longer, later, in the recipe.
Heat a large skillet, melt the butter over medium hight heat. Once the butter starts to sizzle, add the garlic, cooking and stirring until fragrant, approx 30 seconds. Now add the onion, with a small pinch of salt and pepper, and sweat the onion. Once it becomes translucent after a few minutes, add the zucchini noodles with another small pinch of salt and pepper. Cook until the zucchini softens up to your liking. I prefer the zucchini to have a little bite to it, otherwise, it's too mushy once the recipe is said and done.
Once the zucchini has softened, add the pasta and the saffron sauce. Toss until the sauce and zucchini/pasta are well combined. Normally at this stage, there's a good amount of liquid in the pan. Since I undercooked both the pasta and zucchini a little bit, I'll cook everything together for a few more minutes, until most of the liquid gets absorbed into the pasta.
Top will basil, tomato (if using), and parmesan cheese.
Serve and enjoy!