Defrost the frozen phyllo pastry based on the directions on the box.
First prepare the syrup. Put the water and sugar in a pot and bring it to a boil, then reduce the heat and simmer for 20 minutes. In the last minute add the lemon juice.
Let the syrup cool down.
Melt the butter and with a spoon skim the top layer on the butter by taking the milk solids on the surface.
Brush the bottom of a 11 in. x 15 in. glass or metal baking dish with melted butter.
Phyllo pastry dries very quickly so keep a clean damp tea towel or damp paper towels on the pastry to prevent it from drying until ready to use and cover the rest of the pastry after taking each sheet from the pile.
Spread a phyllo sheet on the counter and brush it with melted butter. Sprinkle 2 and 1/2 tbsp. walnuts on the surface.
Roll the phyllo on a very thin Turkish rolling pin or if you don't have one you can use a cake dowel.
After you roll the pastry push each end of roll on dowel until it's squished together.
Push the roll off the dowel and place it in the buttered pan. Repeat until entire pan is filled.
Brush the tops of each roll with melted butter.
Bake the baklava rolls in a 375 F preheated oven for 25 minutes. Then when they are still in the oven reduce the temperature to 325 F and bake for another 30 min. keeping an eye on them. Remove from the oven when they get brown.
Pour the cooled syrup on top of the baklavas with a spoon as they are still hot in the pan.
Let the baklava absorb the syrup and cool down for 4 hours.