Preheat the oven to 375 degrees.
After cutting the spaghetti squash in half lengthwise, remove the seeds with a spoon and discard. Drizzle a tbsp of olive oil and a pinch of salt & pepper on the cut side of the squash and place each half face down on a lined baking sheet. Bake for 40-45 minutes, until you are able to easily stick a knife into the skin.
To make the vegan parmesan, add the cashews, nutritional yeast, garlic powder, and salt to a food processor and pulse until it turns into the consistency of grated parmesan. Transfer to a jar and set aside for later.
To make the pesto, add all of the ingredients except for the olive oil to a food processor. Pulse a few times until everything is pulverized, then leave the processor running while you slowly stream in the olive oil. Start with 1/3 cup, and if it is still too thick for your preference, add a bit more until you reach your desired consistency. Set aside.
Once the squash is done, remove from the oven and let it cool for at least 5 minutes. Use a fork to break up the inside strings of the squash, then add half of the pesto sauce to each half of the squash. Use the fork to stir and combine it with the squash, then spoon some of the vegan parmesan over the top.
You can serve it in the squash boats, or remove it and put it all on a serving dish.