Prepare the syrup.
Combine the sugar, water, and lemon juice in a saucepan. Heat, stirring gently until the sugar dissolves.
Bring to a boil, then stop stirring. Reduce the heat and simmer briefly, about 1–2 minutes. Remove from the heat and set aside to cool while preparing the kunafa.
Prepare the cheese.
If using salty Nabulsi or Akkawi, soak it in cold water in the refrigerator, changing the water several times until pleasantly mild. Drain thoroughly and pat dry before shredding.
Low-salt mozzarella can be shredded and used directly.
Coat the pastry.
Place the thawed kataifi in a large bowl. Cut or pull it into shorter strands, separating any clumps.
Pour over the melted ghee or butter and mix thoroughly until the strands are evenly coated.
Assemble.
Generously grease a 12-inch round baking tray.
Spread half the pastry evenly over the bottom and press into a compact layer.
Distribute the shredded cheese over the pastry, leaving a small border around the edge.
Cover with the remaining pastry and press gently to create an even surface.
Oven Method
Preheat.
Preheat the oven to 350°F (175°C).
Bake.
Bake for 45–60 minutes, until the pastry is golden and crisp and the cheese is melted. Begin checking toward the earlier end of the baking time.
Stovetop Method
Use a suitable tray.
Use a sturdy metal kunafa tray specifically suitable for direct stovetop heat. Do not use glass, ceramic, or a tray intended only for oven use.
Cook the first side.
Place over low heat and rotate the tray frequently using heatproof oven mitts so the bottom browns evenly.
Begin checking after 5–6 minutes, lifting an edge carefully with a spatula. A large tray may take longer, depending on the burner and pan.
Flip and finish.
Remove from the heat. Carefully invert onto another lightly greased, stovetop-safe tray of a suitable size.
Return to low heat and cook the second side, rotating frequently, until golden and the cheese is fully melted. Begin checking after another 5–6 minutes.
Finish and Serve
Slowly pour about 2 cups of the prepared syrup over the hot kunafa, adding it gradually and allowing it to soak in. Use less if you prefer a lighter sweetness.
Let stand briefly, then carefully invert onto a serving platter if desired. Handle cautiously, as the tray and syrup will be hot.
Garnish with finely ground pistachios. Serve warm with any remaining syrup on the side.