In a medium mixing bowl, combine 1 cup all-purpose flour, 1/4 cup granulated sugar, 1 teaspoon baking powder, and a pinch of salt. Whisk together until well-blended, ensuring there are no lumps.

In a separate large bowl, whisk together 3/4 cup of milk, 1 egg yolk, and 3 tablespoons melted unsalted butter until smooth. Gradually combine with the dry ingredients, stirring until just mixed.

While the batter rests, heat oil in a deep skillet or pot to 375˚F. Peel, core, and slice medium apples into 1/4-inch rings and toss with lemon juice.

In a clean bowl, beat 2 egg whites until stiff peaks form. Gently fold the beaten egg whites into the batter.

Dip each apple ring into the batter, allowing excess to drip before frying. Ensure even coating for a crispy exterior.

Lower the coated apple rings into the hot oil without overcrowding the pot. Fry for about 2 minutes per side until golden brown and crispy.

Transfer fried Apple Fritter Rings to a paper towel-lined plate to drain excess oil. Serve hot, optionally dusted with powdered sugar or cinnamon sugar.