Cook your pasta according to package directions, saving at least ½ cup of pasta water before draining.
To a medium-sized pan, add the oil, onion, garlic and cabbage. Saute, uncovered, for 3 to 5 minutes, until the cabbage begins to soften.
Lower the heat, add the water, and cover. Allow to 'steam' for around 5 minutes, until the cabbage softens further and water turns blue.
Remove the cabbage mixture from the heat, and when safe, transfer to a blender with the cashews, additional water, lemon and salt. Blend until a smooth sauce is formed.
Pour the sauce into the cooked pasta and stir until coated completely. Add the pasta water as needed, 1 tablespoon at time, to thin.
