STEP 5: Place the blackberries, sugar, lemon juice, cinnamon stick and lemon zest inside a saucepan. Bring mixture to a boil and cook for 5-6 minutes. Then, stir in cornstarch slurry. Cook until thickened. Refrigerate for 1 hour.
STEP 6: Spread a small amount of frosting onto your cake plate. Place the first layer of cake down. Pipe a circle of frosting just inside the outer edge of your layer to form a "dam" to keep the filling inside.Then, spread an even layer of the blueberry compote inside.