Preheat oven to 350 degrees Fahrenheit. Grease a 9-inch round cake pan with unsalted butter and flour. Set aside while prepping cake batter.
In a large bowl, measure out granulated sugar. Zest 1 tablespoon blood oranges and, using your hands, work the zest into the sugar to infuse it with the flavor of the blood orange zest.
Next, add the ⅔ cup olive oil, the ¼ cup plain Greek yogurt, the 2 eggs, and vanilla bean paste. Whisk everything together until well combined and smooth.
In a separate mixing bowl, sift the Sonora flour, using a food scale to weigh the needed amount. Next, add the baking powder, kosher salt, and ground cinnamon. Stir to combine the dry ingredients together.
Add the dry ingredients to the wet ingredients. Fold gently to combine both the wet ingredients and dry ingredients, taking care to not over mix the batter.
Pour batter into the prepared baking pan. Bake for 30 to 35 minutes until cake tester comes out clean in center and edges of cake are golden.
While the cake bakes, prepare the blood orange simple syrup. In a small saucepan, bring the blood orange juice, sprig of rosemary, and granulated sugar to a boil over medium heat until syrupy, about 2-3 minutes. Remove from the heat and allow to cool slightly. Discard the rosemary sprig.
Once cake is baked, using a wooden toothpick or skewer, pierce the top of the snack cake all over then brush the top of the cake with the blood orange simple syrup.
Cool completely before garnishing with powdered sugar and fresh—or candied—blood orange slices.