In a large bowl, combine 1 cup sugar, flour, tapioca and salt. Add cherries and lemon juice; toss to coat. Let stand for 15 minutes.
Line a 9-in. pie plate with bottom pastry; trim even with edge of plate. Add filling; dot with butter. Roll out remaining pastry to fit top of pie; place over filling. Trim, seal and flute edges. Cut slits in pastry. Brush with milk and sprinkle with remaining sugar.
Bake at 400° for 45-50 minutes or until crust is golden brown and filling is bubbly. Cover edges with foil during the last 15 minutes to prevent overbrowning if necessary. Cool on a wire rack.