Place the onion, zucchini, daikon, cauliflower and garlic into a medium-sized pot, cover with 1 cup of water (235ml) and simmer for 15 minutes over medium heat with the lid on.
After 15 minutes, allow to cool for about 15 minutes and then transfer everything from the pot (including the remaining liquid) to your blender.
Drain and discard the water from the cashews and add the cashews to the blender, along with the nutritional yeast, salt, smoked paprika, ume plum vinegar, brown rice vinegar, and the additional 1/2 cup of water (120ml).
Blend until the sauce is super creamy and smooth, about 2 full minutes.