In a small frying pan heated over medium heat, dry toast the walnuts until fragrant and slightly browned.
Place the walnuts along with the remaining ingredients in a food processor, and pulse until smooth.
Notes
Make sure that your roasted red pepper jar brand does not contain any additional spices, like Cento Roasted Red Pepper. You will find a low FODMAP recipe for harissa on the site. To replace this, use 1/4 teaspoon smoked paprika, 1/8 teaspoon ground cumin and 1/8 teaspoon ground coriander.