· 2 cups all-purpose flour, plus more for dusting· 2 1/4 tsp. kosher salt, divided· 3/4 cup (1 1/2 sticks) chilled unsalted butter, cut into pieces· 1 Tbsp. apple cider vinegar· 1 1/2 lb. heirloom tomatoes, sliced 1/4" thick· 2 garlic cloves, thinly sliced· 4 oz. firm cheese (such as Asiago, cheddar, or Gouda), finely grated (about 1 1/2 cups)· 1 large egg, beaten to blend· Flaky sea salt· Freshly ground black pepper· 1/2 lemon· 1 Tbsp. finely chopped chives
Step 1Preparation Pulse 2 cups flour and 1 1/4 tsp. kosher salt in a food processor to combine. Add butter and pulse until mixture resembles coarse meal with a few pea-size pieces of butter remaining.Step 2Transfer mixture to a large bowl; drizzle with vinegar and 1/4 cup ice water. Mix with a fork, adding more ice water by the tablespoonful as needed, just until a shaggy dough comes together. Turn out onto a work surface and lightly knead until no dry spots remain (be careful not to overwork). Pat into a disk and wrap in plastic. Chill at least 2 hours.Step 3Preheat oven to 400°F. Gently toss tomatoes, garlic, and remaining 1 tsp. kosher salt in a large bowl. Let sit 5 minutes (tomatoes will start releasing some liquid). Drain tomato mixture and transfer to paper towels.Step 4Unwrap dough and roll out on a lightly floured sheet of parchment paper to a 14" round about 1/8" thick. Transfer on parchment to a baking sheet. Scatter cheese over dough, leaving a 1 1/2" border. Arrange tomatoes and garlic over cheese. Bring edges of dough up and over filling, overlapping as needed to create about a 1 1/2" border; brush dough with egg. Sprinkle tomatoes with sea salt and pepper. Chill in freezer 10 minutes.Step 5Bake galette, rotating once, until crust is golden brown and cooked through, 55–65 minutes. Let cool slightly on baking sheet. Finely grate zest from lemon over galette; sprinkle with chives.Step 6Do Ahead: Dough can be made 2 days ahead. Keep chilled.