Preheat oven to 400 degrees F.
Unroll one roll of pie dough and line a 9 inch ungreased deep dish pie plate as directed on box. If you are woried about a soggy bottom, brush some beaten egg over the pie dough.**
In a large bowl, toss the blueberries with the lemon juice.
In a second bowl, thoroughly mix together both sugars, cinnamon, salt, and flour. Pour dry mixture into the bowl with the berries and toss to coat. Empty the coated berries into the dough lined pie dish. Scatter bits of butter over the top of the berries
Unroll second roll of dough and lay over the berries. Seal edges and crimp. Cut slits in top of dough.
Brush dough with some of the lightly beaten egg. Sprinkle with sugar.
Place pie on center rack of a hot oven. To be safe, place a cookie sheet on lower rack in case there are drips (I didn’t have any). Bake pie for 40 minutes or until top is golden brown.