01 -
In a large mixing bowl, whisk together the flour and kosher salt. Add the cold diced butter and use fingertips to work the butter into the flour until the mixture resembles coarse crumbs with pea-sized butter pieces. If butter softens, chill the bowl briefly.
02 -
Drizzle in the apple cider vinegar and 60 milliliters of ice water. Use a fork to toss the liquid into the dry mixture until a shaggy dough forms. Shape into a disk, wrap tightly in plastic wrap, and refrigerate for at least 2 hours.
03 -
Preheat oven to 200°C. Sprinkle the sliced tomatoes with salt and set them on a paper-towel-lined plate to drain excess moisture. In a medium skillet over medium heat, render bacon until crisp, 8–10 minutes. Drain on a paper towel and allow to cool before breaking into bite-size pieces.
04 -
On a lightly floured sheet of parchment paper, roll the dough into a rough 35 cm circle, about 3 mm thick. Arrange tomato slices and bacon pieces over the center, leaving a 4 cm border. Fold dough edges over the filling to form rustic pleats. Brush crust with beaten egg and season with salt and pepper; chill for 10 minutes.
05 -
Transfer galette on parchment to a baking sheet. Bake until the crust is deeply golden and cooked through, 50–60 minutes. Let cool slightly on the baking sheet.
06 -
Transfer galette to a serving platter or cutting board. Top with arugula, drizzle with extra-virgin olive oil, and finish with flaky sea salt before slicing and serving.