Preheat the oven to 350°F and grease a 6x8-inch baking dish.
In your baking dish, whisk the egg. Add the pumpkin, yogurt, oil, maple syrup and vanilla and stir until smooth.
Add the chia seeds. Stir thoroughly to combine.
Add the flour, pumpkin pie spice, baking powder, baking soda, and salt. Stir until just combined, scraping the corners so there are no pockets of dry flour.
Spread the batter out so it's even in the dish. Bake for 30 minutes, until the top springs back and a toothpick in the centre comes out clean.
Let the cake cool before slicing it into squares.
Top with a peanut butter-yogurt drizzle!