Preheat an oven to 160c (320f) and prepare a 9 by 13 inch baking pan with softened butter.
Thaw phyllo dough according to the package instructions. My favorite way is thawing it in the fridge overnight.
In a medium mixing bowl, add the ground pistachios and the cinnamon. Mix until well combined. You can ground the pistachios in a food processor or in a blender until fine mixture forms.
Trim the phyllo dough to fit in your baking pan. Add 7 sheets of phyllo dough into the pan, and brush every sheet of dough with melted butter.
Sprinkle ⅕ of the pistachio mixture on top of the buttered phyllo and spread it evenly. Top the pistachio mixture with another 5 sheets of phyllo sheets, buttering every sheet with melted butter.
Repeat four times until you run out of pistachios. Top the last batch of pistachios with more 5 sheets of phyllo and brush with butter.
Use a sharp knife to cut the baklava into 4 rows lengthwise, and then cut diagonally so that each piece of baklava is in the shape of a diamond.
Bake in a 160c (320f) preheated oven for 1 hour or until the baklava is golden brown.
In a medium saucepan, add the sugar, honey, water, vanilla extract, and lemon juice and cook over medium-high heat mixing constantly until the sugar melts.
Then reduce the heat to medium-low, and simmer for another 4 minutes. Remove from the heat and let it cool.
Remove the baklava from the oven and immediately drizzle the honey syrup all over the baklava.
This will ensure your baklava stays crispy and does not get soggy. Let it cool at room temperature for at least 4 hours and let the baklava soak the syrup.