Preheat your oven to 350°F (175°C). Grease a 9-inch springform pan with butter and line the bottom with parchment paper—this helps the cake release cleanly.

In a large mixing bowl, whisk together both flours, granulated sugar, brown sugar, baking powder, salt, and 1 teaspoon of cinnamon until well distributed. In a separate bowl, beat the eggs lightly, then stir in milk, Greek yogurt, melted butter, and vanilla until smooth. Pour wet ingredients into the dry mixture and fold gently until just combined.

Scoop 1 cup of the plain batter into a small bowl and stir in the remaining teaspoon of cinnamon—this becomes your cinnamon “swirl” batter.

Spread half of the plain batter into the prepared pan, dollop half of the cinnamon batter over, then sprinkle ¾ cup of blueberries evenly. Add remaining plain batter, repeat with cinnamon dollops, and swirl with a butter knife for that classic cinnamon-roll pattern. Top with the rest of the blueberries, gently pressing them into the batter.

Bake for 35–40 minutes, or until a toothpick inserted into the center comes out with moist crumbs. You’ll know it’s done when the edges pull away slightly and the top looks golden.

While the cake cools in the pan for about 10 minutes, whisk the powdered sugar and milk until pourable—adjust consistency as needed. Drizzle the glaze over the warm top, let it set for 15 minutes, then slice into 8–10 pieces and serve.