- With the rack in the middle position, preheat the oven to 150 °C (300 °F). Butter a 33 X 23-cm (13 X 9-inch) baking dish.
- In a saucepan, bring all the ingredients to a boil and stir until the sugar has dissolved. Let cool and refrigerate.
- In a food processor, finely chop the almonds and pistachios. Set aside in a bowl. Chop the walnuts separately because they are softer and change rapidly into an oily paste if they are over processed. Transfer to the bowl with the almonds and pistachios. Add the sugar and cinnamon. Stir to combine. Set aside.
- On a work surface, brush four sheets of phyllo dough with butter and place into a pile. Fold the dough in half crosswise to form a rectangle the same size as the baking dish and place in the bottom of the dish. Cover with a third of the nut mixture.
- Brush two more phyllo dough sheets with butter and pile and fold in half in the same way. Place in the dish and cover with a third of the nut mixture. Repeat the same operation with two more sheets of phyllo dough and the remaining nuts. Top with the four remaining sheets, repeating the same operation of step 3. Brush with butter.
- With a sharp knife, cut the baklava lengthwise into five bands. Cut into eight strips on the diagonal. Bake for about 1 hour and 15 minutes or until the pastry is golden brown.
- Remove from the oven, pour the cooled syrup over the entire surface of the baklava and remove the zest and spices. Let cool at room temperature for about 6 hours or overnight.