Step 1: In a large bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, ground cinnamon, and ground nutmeg until well combined.
Step 2: In a separate medium bowl, whisk the pumpkin puree, milk, vegetable oil, egg, and vanilla extract until smooth.
Step 3: Gradually add the dry ingredients to the wet ingredients, mixing gently until just combined. A few lumps are okay; overmixing will result in tough pancakes.
Step 4: In a small bowl, combine the melted butter, brown sugar, and ground cinnamon. Mix until a smooth, thick paste forms.
Step 5: Heat a lightly greased griddle or large non-stick skillet over medium heat.
Step 6: Pour about 1/4 cup of pancake batter onto the hot skillet for each pancake. Immediately after pouring the batter, drizzle about a teaspoon of the cinnamon roll swirl mixture over the top of each pancake in a spiral or zig-zag pattern.
Step 7: Cook for 2-3 minutes per side, or until bubbles form on the surface and the edges look set. Flip carefully and cook until golden brown and cooked through.
Step 8: Transfer cooked pancakes to a plate. Garnish with a sprinkle of powdered sugar, chopped walnuts, and a drizzle of maple syrup, if desired.
Step 9: Serve immediately and savor every warm, spiced bite!