Preheat the oven to 375°. In a large bowl, toss the apples with the lemon juice. Sprinkle on the brown sugar, flour and salt and toss well. Divide the apples between the lined pie pans. Moisten the pie-shell rims and cover with the dough rounds. Trim any overhang and crimp the edges to seal. Cut 4 steam vents in each pie.