In a large bowl, mix flour, sugars, baking powder, baking soda, salt and pumpkin pie spice. Set aside.
In a separate bowl, mix pumpkin, eggs, vanilla and 1.5 cups of the buttermilk. Add to dry ingredients and whisk together. Add remaining ½ cup buttermilk in small amounts until you reach the consistency you like. Batter should be quite thick, but slightly runny. If you like thinner pancakes, add more buttermilk until you reach the consistency you prefer.
Preheat a griddle on med-high heat and lightly coat with butter.
Spoon batter onto griddle, approximately ¼ cup per pancake, unless you want larger pancakes.
Cook until you see bubbles forming on the top, then gently flip and cook 1-2 minutes longer.
Serve topped with butter, maple syrup, and chopped pecans, if desired.