This galette makes a glorious appetizer cut into small wedges, and can be served warm or at room temperature. To make ahead by a day, store the cooled galette in the refrigerator, then warm in a low oven for a few minutes before serving. Double the recipe and make two, so you can use up more of the phyllo from the opened sleeve. Phyllo dough typically comes in two sizes: 9x14-inch sheets or 14x18-inch sheets. For this recipe, the smaller sized sheet is preferable. If you have the larger phyllo, simply trim the long side down a few inches so that there isn’t too much phyllo dough around the edges of the galette.
Preheat the oven to 375°F and line a heavy sheet pan with parchment paper.
In a small bowl, combine the labneh, garlic and salt. Set aside.
In a large sauté pan, heat the olive oil over medium heat. Sear the tomatoes cut-side down for about five minutes, or until the tomatoes are caramelized and golden brown. Using tongs, gently place the tomatoes on a plate. Set aside.
If you're using 14x18" phyllo, trim the long side of one stack by a few inches. Cover the opened phyllo dough immediately with plastic wrap and a clean kitchen towel to prevent it from drying out as you work (quickly!). Place one sheet of phyllo on the prepared sheet pan and dab with a thin coat of butter. The butter need not coat every bit of the phyllo perfectly. Place another sheet of phyllo on top of the buttered sheet, but turned a half-turn so that the edges hangs over the straight side of the first sheet. Brush with butter, and repeat with the remaining sheets of phyllo, turning each one a half-turn as it is placed over the last sheet.
Spoon the labeh into the center of the buttered phyllo stack and spread to a 10-inch circle. Arrange the tomatoes, cut-side up, in concentric circles on top of the labneh. Scatter the sliced olives over the tomatoes.
Fold the phyllo edges up over the labneh, tomatoes, and olives to form a rustic 3-inch edge around the top. Dab the phyllo edges generously with the remaining butter.
Bake the tart until the phyllo is golden brown, 25-30 minutes. Drizzle with olive oil and top with herbs. Cool for a few minutes before cutting in wedges.