01 - Preheat oven to 350°F. Generously butter a 9x13 inch baking dish with some of the melted butter.
02 - Combine the chopped walnuts, pistachios, almonds, 1/3 cup sugar, and cinnamon in a large bowl. Mix thoroughly to distribute evenly.
03 - Unroll the phyllo dough and cover immediately with a damp kitchen towel to prevent drying out. Keep the towel covering the sheets you're not currently working with.
04 - Place 8 sheets of phyllo in the buttered dish, brushing each sheet generously with melted butter before adding the next. Work quickly to prevent the phyllo from drying.
05 - Sprinkle approximately one-third of the nut mixture evenly over the phyllo base.
06 - Add 4 more phyllo sheets, buttering each one thoroughly. Spread half of the remaining nut mixture over this layer.
07 - Add 4 additional phyllo sheets, brushing each with butter. Sprinkle the final portion of nuts evenly over the surface.
08 - Top with the remaining phyllo sheets, buttering each layer generously as you stack them.
09 - Using a sharp knife, carefully cut the baklava into diamond shapes or squares before baking. Cut all the way through to the bottom of the dish.
10 - Bake for 35-40 minutes until the baklava is golden brown and crisp. The top should be evenly colored.
11 - While the baklava bakes, combine water, 1.5 cups sugar, lemon juice, honey, cinnamon stick, and orange peel in a saucepan. Bring to a boil over medium-high heat, then reduce heat and simmer for 10 minutes until slightly thickened. Remove cinnamon stick and orange peel. Let the syrup cool slightly while still warm.
12 - Immediately after removing the baklava from the oven, slowly pour the warm syrup evenly over the entire surface. Allow to cool completely in the dish for at least 4 hours so the phyllo absorbs the syrup properly before serving.