Lay zucchini noodles on a clean kitchen towel. Sprinkle generously with kosher salt and set aside.
Preheat oven to 400°F. Warm the olive oil in a Dutch oven or large cast iron skillet over medium heat. Add the onions and season with salt and pepper. Cook, stirring occasionally, until caramelized and jammy, about 20 minutes. Increase heat to medium high, stir in sherry and thyme and simmer until completely reduced, about 5 minutes. Add the soup and cream cheese to the onion mixture and stir until the cream cheese is melted.
Squeeze as much moisture as possible out of the zucchini noodles, and stir them into the onion mixture. Top with the shredded cheese, and transfer to the oven. Bake uncovered until bubbly and golden, 20 to 25 minutes. Serve with extra thyme, if desired.
This nutritional information refers to each serving of the entire recipe and not just the products used as ingredients.