Preheat the oven to 350F and prepare a well-greased loaf pan.
In a large mixing bowl, mash the ripe bananas and mix together the eggs, melted butter, vanilla extract and white sugar.
Once everything is well combined, add in the baking soda, salt, all-purpose flour, and cinnamon.
Give one last mix and fold in the blackberries. Careful not to overmix and remember to scrape the sides then pour the batter into your well-greased pan.
Place the cake in the oven for 1 hour to 1 hour and 15 minutes (depending on your oven) or until the middle is fully cooked when you poke it with a toothpick.
Cool, serve and enjoy!