01 -
In a large bowl, whisk together the flour and salt. Toss in the butter and use your fingertips to work it into the flour mixture until the pieces are about the size of peas. If the butter becomes too soft, chill the bowl for 5 minutes.
02 -
Drizzle in the apple cider vinegar and ¼ cup of ice water. Use a fork to combine the liquid with the dry ingredients to form a shaggy dough. Lightly knead into a ball, shape into a disk, wrap in plastic wrap, and chill for at least 2 hours.
03 -
Preheat the oven to 400°F. Sprinkle the tomato slices generously with salt and place them on a paper-towel-lined plate to drain while cooking the bacon. In a medium skillet, cook the bacon over medium heat until crisp, about 8 to 10 minutes. Transfer to a paper-towel-lined plate, let cool, and break into bite-size pieces.
04 -
On a lightly floured sheet of parchment paper, roll the dough into a 14-inch diameter circle about ⅛ inch thick. Arrange the tomato slices and bacon pieces on the dough, leaving a 1½ inch border.
05 -
Fold the edges of the dough up and over the filling. Brush with egg wash and sprinkle with salt and pepper. Chill for 10 minutes.
06 -
Bake the galette until the crust is golden and cooked through, about 50 to 60 minutes. Cool slightly on the baking sheet before transferring to a cutting board or serving platter.
07 -
Top the baked galette with arugula, drizzle with olive oil, and sprinkle with flaky salt before slicing and serving.