Roast the peppers: Char the red bell peppers over a gas flame, under a broiler, or in a hot oven until the skin blisters and darkens. Transfer to a covered bowl for 10 minutes, then peel, remove the seeds, and drain well.
Toast the walnuts: Place the walnuts in a dry pan over medium heat for 3-5 minutes, stirring often, until fragrant. Let them cool before blending.
Blend the base: Add the roasted peppers, toasted walnuts, breadcrumbs, garlic, olive oil, pomegranate molasses, lemon juice, tomato paste, cumin, smoked paprika, Aleppo pepper, salt, and black pepper to a food processor.
Process the dip: Pulse until the mixture becomes thick and slightly textured. Do not over-blend into a completely smooth paste; Muhammara should have body from the walnuts and breadcrumbs.
Adjust the balance: Taste and adjust with more salt, lemon juice, pomegranate molasses, or chili. If the dip is too thick, add cold water 5 ml at a time until spoonable.
Rest and serve: Let the Muhammara rest for 15 minutes before serving. Spoon into a bowl and finish with olive oil, crushed walnuts, and a light pinch of chili if desired..