Place the phyllo dough in the refrigerator and allow it to thaw overnight before preparing the baklava.

To prepare the sugar syrup, combine the granulated sugar and filtered water in a small saucepan.

Bring the mixture to a boil and allow it to boil for 3 minutes without stirring.

Add the lemon juice and continue boiling for approximately 10 minutes, or until the syrup reaches a light consistency that coats the back of a spoon.

Remove the saucepan from the heat and stir in the rose flower water and orange blossom water.

Allow the syrup to cool completely, then refrigerate until required. The syrup may be prepared up to 2 days in advance.

To prepare the clarified butter, line a fine-mesh sieve with paper towel and position it over a heatproof bowl.

Place the cubed unsalted butter in a saucepan and melt over medium heat until foam begins to form on the surface.

Using a spoon, carefully skim the foam from the top of the melted butter and discard it.

Remove the saucepan from the heat and carefully pour the melted butter through the lined sieve into the prepared bowl.

Allow the clarified butter to cool to room temperature before using. Do not apply hot butter to the phyllo dough, as excessive heat may soften the pastry.

To prepare the pistachio filling, place the whole pistachios and ground cinnamon in a food processor.

Pulse until the pistachios are coarsely ground.

Slowly add 4 tbsp of the prepared sugar syrup and ¼ tsp rose flower water.

Continue pulsing until the pistachios are finely ground and the mixture is evenly combined. Avoid processing the nuts into a paste.

Reserve 2 tbsp of the ground pistachio mixture for decoration.

Preheat the oven to 160°C / 320°F.

Place a baking sheet in the oven while it preheats. The heated baking sheet will assist in keeping the bottom phyllo layers crisp during baking.

Line the bottom of a 9x13-inch / 23x33 cm baking dish with parchment paper.

Unroll the thawed phyllo dough and cut the stack of 20 sheets in half to fit the baking dish, creating approximately 40 smaller sheets.

Cover the phyllo dough with a clean, lightly dampened kitchen towel while assembling the baklava to prevent the sheets from drying out.

Lightly brush the bottom and sides of the prepared baking dish with clarified butter.

Place one sheet of phyllo dough in the bottom of the dish and lightly brush the surface with clarified butter.

Place a second sheet of phyllo over the first and lightly brush with butter.

Continue layering and lightly brushing each sheet until 20 sheets have been arranged in the bottom of the baking dish. Apply the clarified butter sparingly to prevent the lower layers from becoming overly saturated.

Spread the prepared pistachio filling evenly over the bottom phyllo layers, ensuring the mixture reaches the edges and corners of the baking dish.

Place the remaining 20 phyllo sheets over the pistachio filling, lightly brushing each sheet with clarified butter as it is added.

Once all layers have been assembled, refrigerate the baking dish for 10 minutes to allow the butter to firm slightly.

Using a sharp knife, cut the uncooked baklava into approximately 1½-inch vertical strips, ensuring the knife reaches completely through the pastry to the bottom of the dish.

Cut diagonally across the vertical strips to form diamond-shaped pieces. Alternatively, cut crosswise to form rectangular pieces.

Place the baking dish on the preheated baking sheet in the oven.

Bake for 50 to 55 minutes, or until the phyllo layers are puffed, crisp, and evenly golden brown.

Remove the baklava from the oven.

Immediately pour the cold sugar syrup between the pre-cut sections of the hot baklava, allowing the syrup to flow into the layers.

For a less sweet baklava, use approximately half of the prepared syrup rather than the full amount.

Sprinkle the reserved ground pistachios evenly over the top of the baklava.

Allow the baklava to cool completely at room temperature so the syrup can settle into the pastry layers.

Serve at room temperature.