01 - Bring a large pot of salted water to a boil. Cook pasta according to package directions until al dente. Reserve 1/2 cup pasta water, then drain and set aside.
02 - While pasta cooks, heat olive oil in a large skillet over medium heat. Add onion and sauté for 2-3 minutes until softened.
03 - Add garlic to skillet and cook for 30 seconds until fragrant, being careful not to burn.
04 - Stir in zucchini and cook for 4-5 minutes until just tender but still slightly crisp.
05 - Add cherry tomatoes, Italian herbs, red pepper flakes, salt, and pepper. Cook for 4-5 minutes, stirring occasionally, until tomatoes begin to soften and release their juices.
06 - Toss in spinach if using and cook for 1-2 minutes until just wilted.
07 - Add drained pasta to skillet and toss everything together, adding reserved pasta water as needed for a silky sauce. Remove from heat, stir in fresh basil, and sprinkle with Parmesan cheese if desired. Serve immediately.