Position rack in middle of oven. Preheat oven to 325°F. Coat the inside of a 13 by 9-inch (33 cm by 23 cm) pan very well with nonstick spray; set aside.

Stir together the chopped walnuts, sugar, lemon zest, cardamom and cinnamon in a bowl until evenly combined.

Unfold the filo dough, place on a piece of parchment paper and cover with a damp cloth to keep them from drying out. Melt the butter in a small pot and have a pastry brush handy.

Place two sheets of filo in the bottom of the pan, either trimming to fit, discarding any extra, or just kind of scrunch up the long ends (which is what I do). Brush butter all over the top. Add two more sheets, brush with butter, two more sheets and another coating of butter (6 sheets so far). Sprinkle half of the walnut mixture evenly over all, then lay on two sheets, butter the top, two more sheets, butter the top, and two more sheets and butter that last one (now you have 12 sheets total). Scatter the remaining nut mixture over all. Then, with the remaining 6 sheets, assemble as before: 2 sheets, butter, 2 sheets, butter, 2 sheets and finish off with butter.

Use a very sharp serrated knife to cut an 8 by 5 grid of squares, going all the way down to the bottom layer. This technique is very important; take your time to keep the layers intact.

Bake for about 40 to 50 minutes or until golden brown, turning the pan front to back once during baking. Cool pan on rack.

While the baklava is cooling, make the syrup. Simply stir the sugar, water, honey and lemon juice together in a small saucepan, bring to a simmer over medium heat and simmer for several minutes or until it visibly thickens a little bit. Slowly pour the syrup over the cooled baklava, saturating evenly. All to sit for at least 4 hours. Baklava is ready to serve or keep loosely covered with aluminum foil at room temperature for up to 3 days.