Pissaladiere (Onion, Olive, and Anchovy Pizza)

Ingredients

• 1 1/4 cups all-purpose flour
• 1/2 teaspoon salt
• 1/4 cup cold unsalted butter, cut into 1/2-inch pieces
• 2 tablespoons olive oil
• 2 tablespoons water, or as needed
• 3 tablespoons olive oil
• 2 1/2 pounds onions, thinly sliced
• 3 cloves garlic, minced
• 1 small bay leaf
• 1 teaspoon chopped fresh thyme
• 1 tablespoon drained capers
• salt and ground black pepper to taste
• 20 large Niçoise olives, pitted and coarsely chopped
• 16 anchovy fillets