Preheat oven to 350°F. Lightly grease a loaf pan with non-stick spray and line it with a sheet of parchment paper.
In a large bowl, whisk together the flour, sugar, baking powder, and salt. Set aside.
In a small/medium bowl, whisk together the strawberry powder and hot water. Set aside.
In a separate medium/large bowl, whisk together the eggs, kefir, vegetable oil, and vanilla extract.
Gently fold the wet ingredients into the large bowl of dry ingredients just until the flour streaks disappear.
Transfer half of the cake batter from the large bowl into the bowl with the strawberry mixture. Fold it in until it's a smooth strawberry cake batter.
Alternately scoop the vanilla and strawberry cake batters into your prepared loaf pan. Swirl the top using a spatula or knife.
Bake on the middle oven rack until a toothpick comes out clean (about 40-50 minutes). Let it cool in the pan for 10-20 minutes, then transfer to a wire rack to finish cooling.
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Notes
Storage: Store fully cooled loaf in an airtight container at room temperature for up to 5 days or in the freezer for 1 month.Lifeway Kefir: This recipe is sponsored by Lifeway Foods. I love their products and mission! If you can't find their strawberry kefir for this recipe, you can substitute an equal amount of plain kefir or buttermilk.