Preheat oven to 350°F. Spray a 9 inch loaf pan with baking non-stick spray. Line the bottom and 2 sides of the pan with parchment paper. Spray again.
In a mixing bowl, sift the flour. Add in baking powder and salt. Set aside.
2 cups All-purpose flour, 2 ½ teaspoon Baking powder, ½ teaspoon Salt
Using a mixer, beat the butter and sugar on high for 3 minutes.
1 cup Unsalted butter, 1 ⅓ cup White granulated sugar
Add in vanilla and eggs. Beat on high for 2 minutes. Scrape the bowl halfway through.
1 teaspoon Pure vanilla extract, 3 Large eggs
Add in ⅓rd of the dry ingredients and half of the Kiefir. Mix until almost combined. Add in another third of the dry ingredients and the rest of the Kiefir. Then, add in the rest of the dry ingredients.
½ cup Lifeway Kefir Plain Whole Milk
Separate the batter into two bowls. Add in sifted cocoa powder and hot water to one of the bowls. Fold the batter gently until fully combined.
4 tablespoon Dutch process cocoa powder, 1 tablespoon Hot water
Use two 1 oz cookie scoops (or 1 TBSP) and scoop each batter into the pan into a checkerboard pattern. See pictures in post. Do this twice.
Add the rest of the vanilla cake batter and spread evenly on top. Use a teaspoon to scoop the rest of the chocolate cake batter on top. Spread the dollop evenly. Use a butter knife to drag the chocolate into the batter. Don't over mix.
Cover with foil loosely. Bake for 45 minutes. Remove foil. Bake for another 20-30 minutes. The cake is done baking when a toothpick inserted comes out clean.
Let the cake sit for 10 minutes in the hot pan before transferring to a cooling rack. Cool completely before decorating.