Denise Barr, one of the cooks at Hedgebrook, served this cake at the first dinner of my stay. She used fresh raspberries from the garden, and it was so good – simple, buttery, with a damp, nubbly, almost muffin-like crumb – that I dog-eared the recipe later that night. The cookbook calls it a Rhubarb Cake, but you could probably make it with any soft fruit, and when I tasted it, before I saw the recipe in the cookbook, it struck me first as a wonderful butter cake. I hope Denise won’t mind that I tweaked the name. When I made it at home, I thawed out a batch of rhubarb compote that I made last summer and spooned it into the batter, and it was terrific.
Preheat the oven to 350°F. Butter and flour an 8-inch square cake pan.
In a small bowl, whisk together the flour, baking powder, and salt. Pour the milk into a measuring cup or small bowl, and add the vanilla extract. Set aside.
In the bowl of a stand mixer (or with a handheld mixer in a large bowl), beat the butter and sugar until light and fluffy. Scrape down the sides of the bowl with a rubber spatula, and then add the eggs one at a time, beating well after each addition. With the mixer on low speed, add the flour mixture and the milk mixture in three doses each, alternating dry and wet. Mix until just combined; then use the rubber spatula to give the batter a brief final mix, to make sure the flour is absorbed.
If you’re using fresh rhubarb or berries, stir the fruit with the tapioca in a small bowl.
Scoop about half of the batter into the prepared cake pan, and spread it across the bottom. Scatter the fruit evenly over the batter – or, if you’re using rhubarb compote, dollop spoonfuls of it evenly over the batter. Do not press the fruit down. Top with the rest of the batter. Don’t worry if the batter doesn’t fully cover the fruit: it will puff and move a bit as it bakes.
Bake for 35 to 40 minutes, or until a toothpick inserted in the center comes out clean. Cool before slicing into squares and serving.
Note: This cake is best on the day that it’s made, but wrapped tightly and stored at room temperature, it should be fine for at least a couple of days.