Cook pasta according to directions in heavily salted water. 2-3 minutes before it's finished cooking, add the broccoli florets and spinach to the pasta water. Drain and rinse the pasta and veggies together in a colander, and run cold water over it to rinse and cool it off.
Meanwhile, mix the minced garlic (1 clove), kosher salt (1 teaspoon), olive oil (1/3 cup) and lemon juice (about 2 tablespoons) in the bottom of a large bowl. Whisk together until emulsified. Taste, adjust seasoning if necessary. (If you are making this ahead of time, remove half the dressing and reserve for later in a separate bowl or container.)
Add the cooled pasta, broccoli, and spinach to the bowl with the dressing, along with the two diced avocados, pumpkin seeds (1/2 cup), and parmesan cheese (1/4 cup), if using. Toss everything together.
Serve. If making ahead of time: cover, refrigerate, and toss with remaining dressing just before serving. If you have leftovers, an extra drizzle of olive oil and squeeze of lemon juice will help revive it if it's a bit dry.
For a vegan version, be sure to omit the parmesan cheese or use a substitute.
Traditional parmesan cheese may not be suitable for a strict vegetarian diet because it contains animal rennet. If you prefer, you can look for a suitable vegetarian substitute, such as a parmesan made with plant rennet.
This pasta salad serves 7-8 as a side dish, and 4-6 as a light meal.
Ingredient substitutions: arugula or another leafy green may be substituted for the spinach, almonds or another nut or seed may be substituted for the pumpkin seeds, other green veggies may be added such as sprouts or green onions, green beans may be used in place of or in addition to the broccoli, red wine vinegar or apple cider vinegar may be used in place of the lemon juice.