In a large bowl, whisk together flour, dark brown sugar, baking powder, baking soda, cinnamon, pumpkin pie spice, and salt.
In a medium bowl, whisk together buttermilk, pumpkin purée, eggs, melted butter, and vanilla extract until smooth.
Fold wet mixture gently into dry ingredients just until combined (leave a few small lumps) and let batter rest for 5 minutes.
Heat a lightly buttered griddle or skillet over medium-low heat. Pour 1/3-cup portions of batter onto the griddle, cook for 2.5–3 minutes until bubbles form around the edges, flip, and cook for 2 minutes more until fluffy and cooked through. Serve warm with butter, maple syrup, and toasted pecans!