Make Cake: Preheat oven to 350℉. Lightly spray 8” square metal pan with avocado oil spray.
Whisk spelt flour, cornmeal, baking soda, baking powder, and salt in medium mixing bowl. Set aside.
In another medium mixing bowl on medium high, beat yogurt, olive oil, coconut sugar, and vanilla until combined, stopping to scrape sides and bottom periodically. Add whole egg and yolk and beat on medium until blended stopping to scrape sides periodically. Add flour mixture and blend on low until mixed, stopping to scrape side as needed.
Scrape batter into 8” square metal pan and spread evenly. Bake 12-16 min until tester in center comes out with moist crumbs.
Let cool 10 min, loosen sides with butter knife or flat long spatula, and turn cake out onto parchment lined tray. Let cool 10 more min and cover.
While cake is baking, prepare blueberries. Lightly heat honey over low heat until thinned. Remove from heat, stir in rosemary, mint, and seeds from vanilla bean. Cover and let sit 10 min. Toss in blueberries to coat. Refrigerate for 1 hour to overnight.
Prepare Whipped Cream. Beat cream and coconut sugar with mixer on high until slightly past soft peaks.
To serve: Cut cake into 16 squares. Place 1 square on plate and top with whip cream, forming divot in center. Spoon berries and honey into divot and onto sides. Top with sprig of mint if desired.