First line a 9x13 pan with natural parchment paper and preheat oven to 350 F.
Start by mixing GF flour for cake, baking powder, baking soda with cinnamon and nutmeg. Add salt and zest of lime to bowl and stir to combine. Wet ingredients can then be added starting with maple syrup, vanilla and chia eggs. Slowly stir in coconut oil and do not over combine.
Separately add the lime juice to the coconut milk and then gently fold in together. Once all ingredients are combined add cake mix to the pan by spreading it out evenly. At this point add the mango and blueberries to the top and gently press them in a bit.
Now combine ingredients for crumb by combining all together and using fingers to create the crumble texture to then scatter on top of the fruit and cake.
Bake for 40-50 minutes and then enjoy!