Preheat air fryer to 410 °. In a large bowl, combine flour, sugar, baking powder, cinnamon and salt. Add milk, eggs, lemon juice and 1 teaspoon vanilla extract; stir just until moistened. Fold in apples. Line air-fryer basket with parchment (cut to fit); spritz with cooking spray. In batches, drop dough by 1/4 cupfuls 2 in. apart onto parchment. Spritz with cooking spray. Cook until golden brown, 5-6 minutes. Turn fritters; c ontinue to air-fry until golden brown, 1-2 minutes. Melt butter in small saucepan over medium-high heat. Carefully cook until butter starts to brown and foam, about 5 minutes. Remove from heat; cool slightly. Add confectioners' sugar, 1 tablespoon milk and remaining 1/2 teaspoon vanilla extract to browned butter; whisk until smooth. Drizzle over fritters before serving.