Soak the cashews in a bowl covered in water overnight. Strain and rinse.
Add all the ingredients into a high-speed blender and blend on high for 45 seconds to a minute, or until very smooth and creamy.
Store in a glass jar in the fridge for up to 10 days!
Because this recipe yields 3 cups of mayo the onion powder and garlic powder proportions may seem excessive. Feel free to add less of these spices when you blend and adjust to your personal tastes.