Cinnamon-Brown Sugar Pop-Tart® Cake

Ingredients (14)

• + cooking spray add to pantry
• + 6 cinnamon-brown sugar toaster pastries (such as Pop-Tarts®) add to pantry
• + 5 tablespoons unsalted butter, melted add to pantry
• + ¾ cup brown sugar, divided add to pantry
• + 1 tablespoon all-purpose flour add to pantry
• + 4 teaspoons ground cinnamon, divided add to pantry
• + 1 teaspoon milk add to pantry
• + ½ cup white sugar add to pantry
• ✓ 1 egg, separated
• + 1 ½ teaspoons vanilla extract add to pantry
• + 1 ½ teaspoons baking powder add to pantry
• + ½ teaspoon salt add to pantry
• ✓ 1 ½ teaspoons white vinegar
• + 1 cup cream cheese frosting, or to taste add to pantry