Prepare the nut filling: Combine the ground pistachios, walnuts, almonds, sugar, and cardamom. Add the rose water and mix until combined. Keep the mixture crumbly rather than turning it into a paste.
Make the syrup: Combine the sugar and water in a saucepan. Bring to a gentle boil and stir until the sugar dissolves. Reduce the heat and simmer for several minutes. Add the lemon juice, then remove from the heat and stir in the rose water. Set aside to cool.
Prepare the phyllo: Carefully unfold the phyllo sheets and cover the unused sheets with a clean, slightly damp kitchen towel to prevent them from drying out.
Build the first layers: Lightly butter a baking dish. Place a sheet of phyllo in the dish and brush it with melted butter. Repeat with several sheets.
Add the filling: Spread a thin, even layer of the nut mixture over the phyllo. Continue layering phyllo, butter, and nut filling until the ingredients are used, finishing with several sheets of phyllo.
Cut the Baghlava: Using a sharp knife, cut the assembled pastry into diamonds, squares, or rectangles before baking.
Bake: Preheat the oven to 350°F (175°C). Bake for 40–50 minutes, or until the Baghlava is deeply golden and crisp.
Add the syrup: Remove the hot Baghlava from the oven and slowly pour the prepared syrup evenly over the pastry, making sure it reaches the cuts and edges.
Rest: Allow the Baghlava to rest for several hours so the syrup can absorb and the flavors can develop.
Garnish and serve: Sprinkle with chopped pistachios, crushed walnuts, or a little cardamom before serving.
