Martha made this recipe on Martha Bakes episode 407.
Preheat oven to 400 degrees. Mix together nuts, 1 cup sugar, 1 tablespoon rose water, and cinnamon in a medium bowl; set aside.
Place remaining 2 1/2 cups sugar, water, and lemon juice in a medium saucepan over medium-high heat. Bring to a boil; immediately reduce to a simmer and cook until slightly thickened, 3 to 5 minutes. Add remaining tablespoon rose water and return to boil; cook 1 minute. Remove from heat and let syrup cool completely.
Brush a 9-by-13-inch baking dish with clarified butter. Carefully layer half the phyllo dough in baking dish, brushing between each layer with clarified butter. Sprinkle nut mixture over top and continue layering remaining phyllo dough over nut mixture, brushing between each layer with clarified butter.
Brush top layer generously with clarified butter. Using a sharp knife with a very thin blade (such as a boning knife), score baklava into 1 1/2-inch-wide diamond-shaped pieces, cutting through all phyllo layers.
Transfer to oven and bake 10 minutes. Reduce heat to 300 degrees and continue baking until golden brown, about 50 minutes more. Remove from oven and pour syrup over baklava; let cool completely before serving.