Preheat oven to 350F. Line a 9-by-10-inch baking pan with parchment paper so the edges of parchment paper stick up (this way you can lift the bars out to cut when they are done); set aside.
In a medium sized bowl make the crumb topping by mixing together the flour, cinnamon, sugars and butter in a bowl. Cut the butter into the dry mixture until sandy. Place in the fridge until ready to use.
In a large bowl, whisk the brown sugar, eggs, and vanilla until smooth.
Pour the melted butter into the brown sugar mixture and whisk until smooth (make sure the melted butter isn’t very hot, or it may cook the eggs)
Add the flour, baking powder, cinnamon and salt and stir until just combined, don’t overmix.
Spread the batter out into prepared pan, smoothing the top lightly with a spatula.
Bake for 20 minutes.
While baking, make the peach filling.
In a bowl, combine all the ingredients for the peach filling, mix and let sit.
When the base has baked for 20 minutes, remove from oven and using a slotted spoon, place the peach mixture over the base, being sure to get as little liquid as possible (or else the bars will be soggy)
Top with crumble topping and bake for another 15-20 minutes until the top is set and lightly browned and the peach filling is bubbly around the edges.
Allow to cool fully before cutting into squares.