Prep meatballs and squash: Make and cook the meatball recipe if you haven’t done so already. For the squash, cut off the stem and bottom of the squash, cut in half and scoop out seeds, cut into 1” thick wedges. Place on a sheet tray and toss with olive oil and kosher salt. Arrange so a cut-side is down against the tray for each wedge.
Roast at 425˚F for 15 minutes. Remove from the oven, flip the wedges, and return to the oven for another 5 to 10 minutes. Squash should be tender but not falling apart and have a good browning color.
To make the soup: Heat a large pot over medium heat with 2 tablespoons olive oil. Add in the diced onion and salt, stirring to coat the onions in oil. Cook for 12 to 14 minutes, until the onions are just starting turning golden and softening. Stir in the orzo and 8 cups of the vegetable broth. Bring to a boil, reduce to a simmer, and cook until the orzo is just al dente, 6 minutes or so.
Once the orzo is mostly cooked, stir in the cooked meatballs and roasted squash. Let simmer for another few minutes until the orzo tender and the meatballs/squash are hot. Now is a great time to add more vegetable broth and taste to adjust salt if needed.
To Finish: Remove the pot from the heat and stir in the dill, lemon zest, and juice from one lemon. Taste and add more dill or lemon juice if desired. You can also serve with extra dill and wedges of lemon on the side so each person can adjust as desired.