Preheat the oven to 375 degrees. Line a baking sheet with a silpat mat.
Place the apple slices into a bowl and sprinkle the lemon juice on them and gently toss to coat the slices with the juice.
Add the sugar, cornstarch, cinnamon and nutmeg to the apples then toss to coat each slice of apple evenly.
Place the apple slices in a spiral inside the pie crust starting one inch from the edge.
Fold the edge of the dough over the fruit.
Brush the dough with the beaten egg. Sprinkle the edges with the raw sugar.
Add the diced butter to the top of the apples.
Place into the oven and for 40-45 minutes, or until golden brown. Remove the galette from the oven and let cool for 10-15 minutes before slicing.
Make the apple cider caramel sauce while the galette is baking. Click here for the recipe.
Serve with the warm caramel sauce drizzled on top and with vanilla ice cream, if desired. Enjoy.