Preheat the oven to 350 degrees. Prepare a 9x13 baking dish (if you use nonstick spray, parchment paper etc)
In a bowl, mix together the starter, melted butter, eggs, and vanilla. Add the white and brown sugar and mix thoroughly.
Add in the flour, baking soda, cinnamon, and salt. Mix until it’s incorporated but don’t overmix. Pour into your prepared 9x13 pan.
In a separate bowl, combine the topping ingredients until crumbly. Sprinkle over the top.
Bake for 40-45 minutes or until it’s baked through.
Let it cool for at least 15 minutes before slicing in to serve.