Preheat the oven to 350° F.
Prepare your 6 cup mini bundt pan using baking spray and make sure to get every single nook and cranny so that the cakes don't stick.
In a small bowl, combine the flour, baking powder, baking soda, salt, and set aside.
In another small bowl, add the blueberries and strawberries and a tablespoon of flour and mix, then set aside.
In a medium bowl, combine the sugar and lemon zest and mix together with your fingers to infuse the sugar with the zest.
Add the room temperature unsalted butter to the sugar/zest and using a hand mixer beat them together until creamed, for about 3 minutes.
Add the eggs one at a time, making sure to beat and incorporate between additions. Then add the sour cream and continue beating. Add the lemon juice and vanilla extract and beat until incorporated.
Slowly add the dry ingredients and beat until just combined.
Add the berries to the batter and fold using a spatula until combined. Don't over mix.
Divide batter evenly into mini bundt pan and fill about ⅔ of the way.
Bake for 15-20 minutes until a toothpick inserted in the center comes out clean.
Let cool completely before inverting onto a cooling rack. Before inverting, you may need to use a offset spatula or knife to loosen the cake.