Preheat the oven to 350º F and line a 9" springform pan with parchment paper. Cover the bottom with parchment paper, then snap the pan back together and trim the excess. Spray the sides and bottom of the pan with cooking spray and set aside.
Whisk together the eggs and honey until they are fluffy and have turned a pale yellow. Add the remaining wet ingredients and beat well.
Add the dry ingredients and mix until just combined. Fold in the lemon zest.
Transfer the batter to the greased pan and bake for 20 minutes, then cover with foil, and bake for another 20 minutes until a cake tester inserted in the center comes out clean.
Cool the cake before removing the springform pan.
Add the blackberries into a small saucepan and heat over medium heat. Cook until you can mash them with a fork and then remove from the heat.
In a small bowl, whisk together the powdered sugar and lemon juice. Pour the glaze over the cake and spread it out with the back of a spoon. Place the mashed berries in the center and allow the juices to mix with the glaze.
Slice and serve with whipped cream, ice cream, fresh berries, a drizzle of honey, etc.