Preheat the oven to 350°F (175°C). Grease the baking dish with a little oil or cooking spray.
In a large mixing bowl, combine the pumpkin puree, maple syrup, applesauce, eggs, and vanilla extract. Whisk until smooth.
In another bowl, mix together the cinnamon, nutmeg, ginger, salt, rolled oats, almond flour, and baking powder.
Gradually add the dry mixture to the pumpkin mixture, stirring until fully combined.
Pour the pumpkin batter into the prepared baking dish and spread evenly with a spatula. If using, sprinkle chopped nuts on top.
Bake in the preheated oven for 30 minutes, or until the edges are firm and the center is set.
Allow to cool for a few minutes before slicing into squares and serving.
Optionally, top with a dollop of Greek yogurt or whipped coconut cream for extra creaminess.