Bring about 1-inch of water to a simmer in a large saucepan. In a mixer fitted with a whisk attachment, whisk the eggs and sugar together until very light yellow and fluffy. Whisk in the lemon juice and lemon zest. Rest the mixing bowl in the saucepan with the bowl's base above the simmering water (pour out some of the water if necessary.) Cook, whisking occasionally, until the mixture is thick and custard like, about 15 minutes. Remove the bowl from the heat and stir in the butter. Let cool, cover, and refrigerate overnight. Squeeze a dab of meringue on each of 8 plates and press one phyllo triangle down on it. Spoon a heaping tablespoon of lemon curd in the center, then pipe on some meringue. If possible, brown the meringue with a blowtorch. Place another phyllo triangle on top and repeat, topping off with a final phyllo triangle. Garnish with a mint sprig, a dusting of powdered sugar, and raspberry puree, if desired.
In a mixer fitted with a whisk attachment (or using a hand mixer) and a clean dry bowl, whip the egg whites until soft peaks form. Add the brown sugar and continue whipping until stiff and glossy, about 30 seconds more. Gently spoon meringue into a pastry bag fitted with a plain tip.
Preheat the oven to 350 degrees F. Line a large sheet pan with parchment paper. Place 1 sheet of phyllo on the pan and brush with melted butter. Sprinkle evenly with 2 tablespoons of the sugar and then place another sheet of phyllo on top. Brush with melted butter, sprinkle with sugar, lay another sheet of phyllo on top, and brush with melted butter, and sprinkle with sugar. Repeat on another sheet pan with remaining 3 sheets of phyllo, butter, and sugar. You should have 2 stacks of phyllo dough, each 3 sheets thick. With the tip of a sharp knife, cut each stack into 12 triangles. Cover both stacks with parchment paper. Place one of the pans on top of the other to weight it down. Then place another empty sheet pan on the very top (this is to keep the phyllo from buckling during baking). Bake 10 to 12 minutes, until the phyllo is golden brown. Remove the whole stack of sheet pans and let cool (do not unstack the pans).