Add the cashews to a small bowl, then add the boiling water (make sure the cashews are completely submerged in the water).
Let the cashews soak for a minimum of 1 hour (a maximum of 12 hours is fine too).
When the cashews are done soaking, strain and rinse them, discarding the liquid.
Begin to cook the gluten-free pasta according the instructions on the package. Be sure to opt for the al dente timing because you’re going to be cooking the pasta with the sauce for a few extra minutes after you’ve drained it. If there is no al dente instructions on the package then subtract 1-2 minutes from the cooking time to ensure the final result isn’t overcooked.
While the pasta is cooking, add the cashews to a blender or food processor along with the tomatoes, garlic, salt, and pepper, then blend until smooth. Scrape down the sides of the blender or food processor as necessary and pause every 30 seconds to ensure the machine doesn’t overheat. It may take a few minutes to get a very smooth consistency.
Once the pasta has finished cooking, strain it and discard the water, then add the pasta back to the pot.
Add the blended cashew tomato sauce to the pot with the pasta, then stir to coat the pasta with sauce.
Place the pot on the stove set to low-medium heat and cook for 2-3 minutes to heat up the sauce and to allow the raw garlic to cook.
Remove from the heat, then garnish with fresh chopped basil and/or crushed red pepper flakes, if desired, before serving.