Blackberry Upside Down Cake

Let be start by saying that when assembling this cake, I was sure that the cake batter was not going to adequately cover the topping.

SURPRISE

Original Recipe from Allrecipes.com and says it was submitted by PamelaP.  I initially was thinking I needed to do something to get the thick batter to better/more evenly cover the topping. Not so sure  that  is needed now.

INGREDIENTS

TOPPING                                                                                           CAKE

1/4 Cup Brown Sugar                                                                         1 Cup White Sugar

2 TBL Spoons Unsalted Butter                                                           1/2 Cup softened butter

2 Cups fresh blackberries                                                                   2 Eggs

3/4 Cup white sugar                                                                           1 1/2 Cup all purpose flour

                                                                                                           2 TSP baking powder

                                                                                                           1/2 TSP salt

                                                                                                           1/4 Cup milk 

                                                                                                           1 TSP vanilla extract

PUTTING IT TOGETHER

1. Preheat oven to 350 degrees
2. You will  need a 9 inch cake pan ( non-stick if you have it)
3. Melt brown sugar and butter in saucepan, over medium heat.  Add blackberries to brown sugar mixture; cook and stir until mixture bubbles ( 1 to 3 minutes). Stir in 3/4 cup white sugar into berry mixture. Crush berries slightly while stirring, continue cooking until berries are hot and slightly broken down,  ( about 5 minutes ). Remove from heat and pour into cake pan.
4. Beat 1 cup white sugar and the 1/2 cup butter in a bowl with electric mixer until light and fluffy
5. Whisk together dry ingredients in a bowl.  Alternately add dry ingredients and milk beginning and ending with flour. Then mix vanilla into batter. (see no reason not to add this to butter/sugar/egg mixture)
6. Pour batter over blackberry topping. Now I just have to interject here that this batter does not pour. Which was the cause of my initial concern.  So Spoon batter over topping and without blending batter and topping smooth together batter clumps the best you can.  Do not worry about getting all the topping covered. I did not and see the picture above.
7. Bake in your preheated oven for 35 to 40 minutes . Allow cake to cool for up to 30 minutes. Loosen cake from sides of pan. Invert onto a plate larger that the pan,( so a 12 inch plate,  topping will drip down sides). Lift pan slowly to release cake. 

My cake fell, could be I did not let cake cool long enough.

 As a result the topping pooled in the  middle, which then soaked  the middle of the cake.  Causing the very center of a wedge of cake to be mushy, flavorful but mushy.

I am considering; trying this is a small bundt pan.  

Cooking it to the 40 minute mark ( at 35 minutes my cake passed the toothpick test )

Perhaps adding a tsp of  butter flavoring to the topping.

And I think it could use a touch of cinnamon in the topping.