Heat oven to 350F and thoroughly grease a tart tin.
Mix the oat flour, pepita flour, cinnamon, and salt in a large bowl, then add the vanilla, coconut oil, and maple syrup. Squeeze everything together with your fingers until a dough forms. Press into your greases tart tin, poke some holes in the bottom with a fork, and bake for 10-15 minutes or until it just starts to turn golden.
Mix cranberries, raspberries, maple syrup, orange juice, orange zest, and arrowroot in a bowl. Pour into the tart crust and bake for another 30 minutes or until bubbling.