Boursin cheese adds delicious creaminess to this one-pan, veggie-packed pasta. We use the garlic-and- herbs flavor here, but other Boursin flavors like shallot and chive or cracked black pepper would be just as tasty.
Preheat oven to 400°F.
Toss tomatoes, mushrooms, 2 tablespoons oil, Italian seasoning and crushed red pepper (if using) together in a 9-by-13-inch baking dish. Place Boursin in the center. Bake until the tomatoes are broken down and bubbling, about 20 minutes.
Add pasta and garlic to the baking dish. Sprinkle with salt and pepper. Pour boiling water over the mixture and gently stir. Cover with foil and bake, stirring once, until the pasta is tender, about 20 minutes total.
Meanwhile, place spinach in a medium bowl. Drizzle with the remaining 1 tablespoon oil then massage until its volume is reduced by half. When the pasta is tender, remove the baking dish from the oven and stir again. Add the spinach and stir to combine. (The pasta will be very saucy.) Cover and let stand for at least 20 minutes for the sauce to thicken and the spinach to wilt.