Preheat oven to 400°F. Cut cauliflower into small florets and place in a large bowl. Toss with olive oil and Ras el Hanout. Place florets on the center of an aluminum lined baking sheet. Fold aluminum around the florets and seal closed. Roast in the oven for 20 minutes. Carefully open seal and roast for 10 more minutes. Meanwhile, dry toast the walnuts in a small skillet for 4-5 minutes, stirring. In a food processor, add the toasted walnuts and the remaining Muhammara ingredients. Pulse until finely chopped, but not pureed. Unfold the two sheets of thawed puff pastry sheets and place on a greased baking sheet, overlapping by an inch. Trim to size, if necessary. Using your fingers, dampen both sides of the overlapped portions of the puff pastry sheets and then pinch together. Pinch all edges up to form a crust. With a fork, lightly puncture the pastry sheet every couple inches. Place in 400°F oven and bake for 15 minutes. Remove and spread the Muhammara sauce evenly inside the crust. Top with the roasted cauliflower, sprinkle with Aleppo and bake for 10 more minutes. Remove from oven, slice and serve warm.