Whole Wheat Spinach-Feta Tart

Ingredients

• 3/4 cup (95 grams) all-purpose flour
• 3/4 cup (90 grams) whole wheat flour
• 10 tablespoons (140 grams) unsalted butter, cold, cut into ½ inch cubes
• 1 teaspoon kosher salt
• 1/2 cup cold water
• 1 tablespoon unsalted butter
• 1 tablespoon all-purpose flour
• 1/2 cup whole milk
• 5 ounces frozen spinach (half of a 10 ounce bag), defrosted
• 3 ounces feta cheese (a generous ½ cup), crumbled, divided
• 1 tablespoon tablespoon finely chopped preserved lemon (about ¼ of a medium lemon)
• 1/4 teaspoon freshly ground black pepper
• 1 pinch kosher salt
• 1 pinch crushed red pepper flakes