Preheat oven to 350ºF. In a large bowl, combine the pumpkin, almond butter, honey, eggs, pumpkin pie spice, salt, and baking soda, and stir until very smooth.
Add the vinegar into the batter, and stir again. The batter will have lighter swirls in it, from the baking soda reacting to the vinegar. This will help the bars rise and remove any baking soda flavor in the final bars, so keep stirring until the batter looks uniform. Pour into a greased 8-inch baking dish, lined with parchment paper for easy removal later.
Bake at 350ºF for about 35 minutes, until the bars rise in the center and don't jiggle when you shake the pan. Cool completely, then slice and serve.
To make the optional Maple Pecan Glaze, combine the pecans, maple syrup, coconut oil, water, vanilla, and salt. Blend until very smooth, scraping down the blender as needed. You can add a tablespoon of water, as needed, to help it blend. Pour the glaze over the bars, and serve right away with chopped pecans on top.
Nutrition information is for 1 of 9 bars. This information is automatically calculated, and is just an estimate, not a guarantee. For a lower-calorie treat, slice the bars into 16 squares instead. If you don't have pumpkin pie spice, use 1 teaspoon ground cinnamon, 1/2 teaspoon ground ginger, 1/4 teaspoon ground nutmeg and 1/4 teaspoon ground cloves to replace the 2 teaspoons of pumpkin pie spice.For a vegan, grain-free recipe, try my Vegan & Gluten-Free Pumpkin Bars.