Peel pears. Cut off both ends of pears and cut pears in half lengthwise. Using a melon baller or a carrot peeler, cut off inside core Slice pear halves and place into bowl of water with lemon.
Place paper towels into a large bowl, ring out pears gently from the water and place into bowl. Pat pear slices dry with paper towels.
Add sugar, cornstarch, cinnamon, nutmeg, and salt to the pear slices and gently mix to coat. Pour into premade pie crust and smooth evenly.
In a medium bowl add flour, butter, and brown sugar. Use a pastry blender, food processor, or your finger tips to combine ingredients until a crumble forms.
Sprinkle crumble topping over the pears. Bake at 425 degrees for 15 minutes. Cover loosely with a sheet of foil and bake an additional 15 minutes until pears are soft. Cool pie completely before slicing.
