In a large skillet or pot, bring the salted water to a boil. While waiting, prepare your broccoli by trimming the stems and cutting the florets into bite-sized pieces. Add the rotini pasta and boil on high heat for 4 minutes. Then add the broccoli, cover the pot, and set a timer for 3 minutes, keeping the heat high enough to maintain a rolling boil. When the timer goes off, turn off the heat and drain the pasta using a lid or colander. Return the pasta to the pot and stir in the spinach. Sprinkle with lemon zest and let it sit for a few minutes to allow the spinach to wilt. Meanwhile, melt the 4 tablespoons of butter in a small skillet over medium heat. You can brown the butter if you like, but it’s not necessary. Add the minced garlic and crushed red pepper, sautéing for about 1 minute until fragrant. Remove from heat and stir in 2-3 tablespoons of fresh lemon juice. Pour the lemon butter sauce over the pasta mixture and stir to combine. Mix in 1 cup of fresh Parmesan cheese, drizzle with olive oil, and season with salt and pepper to taste. Garnish with extra Parmesan cheese, fresh lemon wedges, and serve hot.