Preheat the oven to 400 degrees. Cut the squash in half lengthwise and scoop out seeds and anything slimy with a dining spoon. On a sheet pan lined with foil, drizzle each side with olive oil and sprinkle well with salt + pepper. Lay squash cut-side down on the pan and roast for 40 minutes.
When squash has finished roasting, remove from oven and flip the squash over to let cool. Take a fork and run from the top of the edge down to the center (with the grains) to create your strands.
Make sauce:
In a deep skillet over medium heat, warm 1 tbs. olive oil then add in ground turkey. Break up with wooden spoon as it cooks and season with 1 tsp each salt + pepper, plus a pinch of red pepper flakes.
When turkey is cooked, pour in marinara sauce and fold in spinach. Add 1/2 cup mozzarella and 1 tbs. parmesan cheese to mixture.
Add strands from 1/2 the squash to the sauce and mix altogether before stuffing the empty squash boat with the mixture.
Top with remaining cheese and broil to melt, about 5 minutes!