Wash and dry blackberries. Make sure they are at room temperature before beginning the next steps.
Combine cake flour, baking powder, baking soda and fine sea salt into bowl and whisk to combine. Set aside.
1 ¾ cup cake flour, sifted, 1 tsp baking powder, ½ tsp baking soda, ½ tsp fine sea salt
In a large bowl cream softened butter, sugar and vanilla for about 2 to 3 minutes, or until light and fluffy.
¾ cup unsalted butter, softened, 1 cup sugar, 1 tsp imitation vanilla extract
Drizzle in oil and mix on low speed until well combined.
¼ cup canola oil or vegetable oil
Add eggs one at a time and whisk on medium speed until well combined.
3 large eggs
Add ½ of dry ingredients to wet ingredients and whisk on low until just combined.
Add kefir to batter and mix on low until combined.
½ cup raspberry kefir, room temperature
Add remaining dry ingredients and mix on low until some streaks of flour remain.
Add sprinkles and blackberries and use a silicone spatula to fold into batter gently. Only fold in until just dispersed, do not over mix.
½ cup rainbow jimmies, 1 cup fresh blackberries
Preheat oven to 350 F. Butter and flour a 8x8 baking pan, and then pour batter into pan. Use silicone spatula to evenly distribute.
Bake for 45 minutes, or until a toothpick comes out with just a few crumbs. Remove from oven and allow to cool on wire rack.