Preheat your oven to 374°F (190°C). Line a 8x12 inch pan with parchment paper for easy cleanup and removal.
In a large bowl, use a whisk or an electric mixer on medium speed to beat the eggs and sugar for 2-3 minutes. The mixture should become pale, thick, and frothy. This creates a light cake texture.
3 large eggs, ½ cup granulated sugar
Add the kefir, neutral oil, and vanilla extract. Whisk or mix on low speed until the mixture is completely smooth and uniform.
1 cup plain kefir, ½ cup neutral oil (like avocado, canola, or light olive oil), 1 teaspoon vanilla extract
Place a sieve over the bowl and add the flour, baking powder, and baking soda. Sift them directly into the wet ingredients to prevent lumps. Use a whisk or a spatula to gently fold the dry ingredients in. Mix only until the flour disappears; a few small lumps are okay.
2 ½ cups all-purpose flour, 1 teaspoon baking powder, ½ teaspoon baking soda
Pour the finished batter into your prepared pan, using a spatula to spread it evenly.
Arrange your plum halves on top of the batter, gently pressing them in. Place them cut-side up for the best presentation.
1.1 lbs fresh plums, halved and pitted
Bake for 60 minutes. To test for doneness, insert a toothpick into the center of the cake (avoid hitting a plum). If it comes out clean or with a few dry crumbs, it's ready.
Let the cake cool completely in the pan on a wire rack. This is crucial for clean slicing. Once cool, dust the top generously with powdered sugar, slice into squares, and serve.
Powdered sugar
Video
Notes
I always make this dessert with room-temperature eggs and kefir. It helps them mix in smoothly and makes the cake's texture so much better.Be careful not to overmix the batter after you add the flour. Just stir until you no longer see dry pockets. A few lumps are okay and will prevent a tough cake.You can use any kind of fresh plum. If your plums are very tart, I suggest sprinkling the halves with a little extra sugar before baking. This gives you a perfect sweet and tangy bite.To check if the cake is done, poke a toothpick into the cake part, not into a plum. It should come out clean.Let the dessert cool down completely in the pan before you slice it. This is the secret to getting neat, perfect pieces every time.If you don't have kefir, you can use an equal amount of plain yoghurt or buttermilk instead. The cake will still be wonderfully moist.