Heat oven to 400°F. Grease a small size bundt pan with butter and dust with flour.
In a small bowl whisk together the cinnamon and brown sugar.
In a medium bowl, whisk together the flours, sugar, baking powder and salt. Gently stir in the blueberries. In a large bowl, whisk together the egg, yogurt, and coconut oil until thoroughly combined.
Stir the flour-blueberry mixture into the yogurt mixture and stir until just combined. Pour one half of the batter into the bundt pan, sprinkle the cinnamon-brown sugar mixture evenly across it, then top with the remaining batter.
Place pan in the oven and bake for 30-35 minutes, checking after 30 minutes, until a tester inserted in the cake comes out clean.
Remove cake from oven and transfer to a wire rack; let stand in cake pan for 10 minutes then then gently turn out onto the rack to finish cooling completely. Cake can be stored in the fridge, well wrapped, for 3 days.