In a small saucepan, combine 1 1/2 cups granulated sugar, 3/4 cup water, and 1 tablespoon fresh lemon juice.
Bring to a boil over medium heat, stirring until the sugar dissolves.
Reduce heat to low and simmer until the syrup thickens slightly, about 8-10 minutes.
Remove from heat, stir in 1 teaspoon orange blossom water, and set aside to cool completely.
Preheat the oven to 350°F and lightly grease a 9-inch round baking dish.
If frozen, thaw 1 pound kataifi (shredded phyllo) dough, then gently separate or chop the strands.
Place the dough in a large bowl, pour in the melted butter, and toss with your hands to coat every strand.
Press half of the buttered dough into the bottom and up the sides of the prepared dish.
Spread the ricotta cheese evenly over the dough, leaving a 1/3-inch border around the edge.
Top with the remaining buttered dough, pressing down lightly to form an even layer.
Bake until the top is golden brown and the edges are crisp, about 30-40 minutes.
Remove from the oven and immediately pour the cooled orange blossom syrup over the hot kunafa. Let it absorb for 5-10 minutes.
Sprinkle with the chopped pistachios and serve warm.