For the Crust

1. Cut the cold butter into 1/2-inch thick cubes. It should be fresh from the fridge.
2. Combine the flour, salt and butter in a food processor. Pulse several times until the mixture is crumbly, but still has large chunks of butter.
3. Add the egg, vinegar, and 2 teaspoons of ice-cold water. Pulse until the dough begins to hold together. If needed, add additional water 1 teaspoon at a time.
4. Turn the dough out onto the counter. Press it into a ball, then flatten it into a disc about 5 inches wide. Wrap it in plastic wrap and refrigerate it for a minimum of 60 minutes.
5. Roll the dough onto a lightly floured surface, rolling from the center to the edges and rotating occasionally. Roll it out so it’s about 11” in diameter, leaving you at least 1 inch on each side of the pie plate.
6. Place the dough into a 9-inch pie plate and fold under the excess edges, then crimp the edges. Refrigerate the dough while you prepare your pie filling.
7. Preheat the oven to 375°F.

For the Filling

1. Rinse and dry the blueberries. In a large bowl, combine the blueberries with the flour and sugar and toss to coat the berries in the dry ingredients.
2. Zest the lemon and then squeeze the juice over the berries and mix together until well combined. Let the mixture set for at least 10 minutes.

For the Topping

1. Dice the butter into small pieces and combine with the flour, sugar, and cinnamon. Use a pastry cutter or two forks and press the butter into the dry ingredients until it resembles a crumbly mixture and the butter is broken down into smaller pieces.
2. Next, add the rolled oats and cut them into the flour mixture. Once it’s roughly combined, use your hands to start pressing the mixture into larger pieces.
3. Pour your blueberry filling into the prepared crust and then sprinkle the crumble topping over the berries.
4. Bake at 375°F for 60-65 minutes placed on a rack on the lower third of your oven. The filling should be bubbling. Remove from the oven and allow to cool for at least 2 hours.