Preheat oven to 375°F and line an 8x8 baking dish with parchment paper.
In a bowl, mix together non-dairy milk, yogurt, vanilla extract, and coconut sugar.
Add gluten-free flour, baking powder, baking soda, cinnamon, and salt. Stir until well combined.
Fold in the blueberries, then transfer the batter to the prepared baking dish.
In a small bowl, mix together melted butter, coconut sugar, salt, and gluten-free flour to make the streusel topping.
Sprinkle the streusel mixture over the batter, then press down slightly.
Bake for 40-45 minutes or until a toothpick inserted into the center comes out clean.
Allow the cake to cool for 20 minutes before slicing.
Serve as is or with powdered sugar icing or whipped honey.