Step 1: In a large bowl, whisk together the flour, granulated sugar, baking powder, baking soda, and salt for the pancakes. Set aside.
Step 2: In a separate medium bowl, whisk together the buttermilk, egg, 1/4 cup melted butter, and vanilla extract until well combined.
Step 3: Pour the wet ingredients into the dry ingredients. Stir gently with a spatula until just combined. A few lumps are okay; do not overmix, as this will result in tough pancakes.
Step 4: Prepare the brown sugar cinnamon swirl: In a small bowl, combine the 1/4 cup melted butter, brown sugar, 1 tablespoon flour, ground cinnamon, and 2 tablespoons milk. Whisk until smooth. Transfer the mixture to a piping bag or a small resealable plastic bag with a tiny corner snipped off.
Step 5: Heat a lightly greased griddle or large non-stick skillet over medium heat. Pour about 1/4 cup of pancake batter onto the griddle for each pancake.
Step 6: Immediately after pouring the batter, pipe the brown sugar cinnamon swirl mixture in a spiral or zigzag pattern onto each pancake. Use a toothpick or the tip of a knife to gently swirl the cinnamon mixture into the batter once or twice.
Step 7: Cook for 2-3 minutes per side, or until golden brown and bubbles form on the surface, and the edges appear set. Flip and cook for another 1-2 minutes until cooked through.
Step 8: Remove cooked pancakes from the griddle and serve warm with your favorite toppings like maple syrup, powdered sugar, or whipped cream. Enjoy!