Sponge Cake with Rich Lemon Filling | America's Test Kitchen

Ingredients

• 1/2 cup (2 ounces/57 grams) cake flour
• 1/4 cup (1 1/4 ounces/35 grams) unbleached all-purpose flour
• 1 teaspoon baking powder
• 1/4 teaspoon table salt
• 3 tablespoons milk
• 2 tablespoons unsalted butter
• 1/2 teaspoon vanilla extract
• 5 eggs , room temperature
• 3/4 cup (5 1/4 ounces/149 grams) granulated sugar
• 1/4 cup cornstarch
• 1/8 teaspoon table salt
• 1 cup cold water
• 4 large egg yolks
• 2 teaspoons grated lemon zest
• 1/3 cup lemon juice from 2 lemons
• confectioners' sugar for dusting