Make the pesto first. Combine the nuts, cilantro, garlic, extra-virgin olive oil, sea salt, (optional nutritional yeast), lemon juice and black pepper in a food processor, and blend until smooth.
Peel and devein the shrimp before they are cooked, pulling the tail off first, then the rest of the shell. (Doing this before cooking allows you to serve the dish warm, as deveining after cooking would require you let the shrimp cool first.)
Place a steamer basket in a large sauce pot, and boil about an inch of water.
While the water is heating, run a julienne, spiral or regular vegetable peeler along each of the squash until you reach the center, seedy part. Steam the squash for about 3-5 minutes. Set the steamed squash "noodles" aside.
Steam the shrimp for approximately 3 minutes or until they're pink all the way through.
Place the steamed squash into a mixing bowl with the pesto and toss until well combined.
Top the noodles with the shrimp, and serve warm.