Preheat the oven to 350°F. Spray an 11x7 baking dish with cooking spray, and set aside.
In a medium-sized bowl, stir together the flour, baking powder, and salt, and set aside.
Cream the butter with the granulated sugar and brown sugar for 3 minutes. Add the egg and vanilla, and mix to combine.
Add ½ of the flour mixture and stir it in. Add half of the milk and stir it in. Repeat with the remaining flour and milk.
Add the cranberries and mix until just combined. Spread into the prepared baking dish.
In a medium-sized bowl, stir together the brown sugar, flour, cinnamon, and salt.
Pour in the melted butter and stir with a fork to produce crumbs, mix until there are no dry patches left. Sprinkle evenly on top of the batter.
Bake for 40-45 minutes until golden brown and a toothpick inserted into the center comes out clean. Let cool before serving, can be enjoyed warm or at room temperature.
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