If you are using raw cashews and you don't have a high-powered blender, then you must soak them overnight in a bowl of water, drain and rinse. Otherwise, your result will be gritty and NOT creamy. A food processor usually works better with soaked cashews versus a blender that isn't very powerful.
Add your onions and 1 cup of vegetable broth to a large pan over medium to medium-high heat. Cook for about 8 minutes until your onion begins to become very tender, being careful to not let your onions burn.
After 8 minutes, add your garlic into the pan and continue to reduce down for another two minutes, stirring often. Your broth should be evaporated at this point.
Take your onion and garlic mixture and place in a blender. Add the remaining 1/2 cup of vegetable broth to the blender alongside your salt, pepper, raw cashews, and lemon juice. Blend on high for a couple of minutes until the mixture is creamy and smooth. Depending on your preferred taste and consistency you may add more broth, lemon juice, and seasoning.