White Lily Savory Tart Pissaladiere

Name: White Lily Savory Tart Pissaladiere
Ingredients: 2 cups White Lily flour; 1 1/2 teaspoons kosher salt; 6 ounces (1 1/2 sticks) unsalted butter, chilled and cut into 1-inch cubes; 4 to 5 tablespoons whole milk, cold; 2 tablespoons extra-virgin olive oil; 4 large yellow onions, cut in 1/2 through the root and sliced into 1/8-inch-thick slices; Kosher salt; Freshly ground pepper; 2 to 4 tablespoons dry sherry, optional; 3 anchovies, packed in salt and rinsed in cool water, broken into 1/4-inch pieces; 25 to 30 red or yellow cherry tomatoes, tossed in 1 teaspoon olive oil; 25 to 30 assorted pitted black olives (Saracene, Kalamata, or Nicoise); 8 to 10 whole thyme sprigs