Place blueberries in a medium bowl and pour boiling water over top. Allow to soak 10 minutes.
Drain water from blueberries and place blueberries and lemon juice in a food processor. Puree blueberries until smooth and a paste-like consistency.
Preheat oven to 350F and line a large sheet pan with parchment paper.
Remove dough from refrigerator and turn onto a lightly floured surface. Roll dough out into a 12x9 inch rectangle and cut into 3 equal strips length-wise.
Spread blueberry filling down the center of each dough strip to within 1/2-inch of edges. Pinch edges of dough to seal around blueberry filling (refer to blog post for step-by-step photos. Be aware, the dough may crack a little bit during this step - gently pat and roll the dough tube to smooth). Carefully transfer each dough tube to prepared sheet pan and brush well with egg wash.
Bake blueberry newtons at 350F 15-20 minutes until a light golden brown. Allow newtons to cool completely on pan on a wire cooling rack.
Once newtons are cooled, use a sharp knife or benchscraper to cut into 1-inch newtons. Enjoy!