Place flour, sugar, cornmeal and salt into a food processor and pulse a few times to mix together. If using a bowl just whisk together.
Add cold butter in tablespoon size slices and pulse again until crumbly and peas size balls are formed. If doing by hand use a pastry cutter or fork and knife.
Slowly add buttermilk thru the liquid shoot and continue blending until a ball of dough forms. If not completely coming together you can always add just a tablespoon more of buttermilk.
Place ball of dough into plastic wrap and chill for an hour or longer.
Assembling:
When ready to assemble preheat over to 375 F.
In a medium bowl stir together all of the filling ingredients. Allow to sit and rest for a bit for the juices to have a bit of time to thicken.
Place chilled dough on a piece of parchment paper that has been sprinkled with flour. Roll out the dough to a large 12-14 inch circle. It does not need to be perfectly round. This galette has more of a rustic look. Place the parchment paper with the dough onto a large cookie sheet.
Place the filling inside of the circle and then fold the edges up all around the filling. Overlaping as needed.
Whisk egg and brush along the top of the dough and then sprinkle with turbinado sugar.
Bake for about 45 minutes, or until the crust is a nice golden brown and the filling is bubbling.
Allow to cool for about 20-30 minutes before serving. Serve with vanilla ice cream or whip cream for the perfect dessert.
Notes
Some of the liquid may seep out a bit from the sides of the crust, but it's fine. This is a more rustic style pie that is not supposed to look perfect.I have given both cups and grams as measurements. Grams will be more precise, especially when measuring flour. If you don’t have a kitchen scale, no problem! Just lightly spoon flour into your measuring cup to insure its not packed in there. Light and fluffy is the key.