Place the raw cashews into boiling water and allow to soak for 20 minutes, then drain. In the meantime, heat the olive oil in a non-stick pan and saute the onions and garlic until soft. Sprinkle in the salt to speed up the process.
Place your red peppers over an open flame, turning regularly, until the skin is blackened - or alternatively, place it under the grill for 20-25 minutes. Allow for the peppers to cool down for 10 minutes, then gently peel off the skin, slice them in half and remove the seeds.
Prepare your pasta according to packaging instructions.
Transfer the peppers, onions & garlic and softened cashews to a blender and blend them alongside the tomato puree, nutritional yeast and 60ml of pasta water until smooth. Season to taste with salt and pepper and heat the sauce over medium heat, then add in your ravioli and serve garnished with fresh herbs.