Remove the cake from the oven and immediately — while it is still hot — poke holes all over the surface using a wooden skewer, a toothpick, or a fork. Make the holes generously and distribute them evenly across the entire surface, including close to the edges and into the corners. The holes allow the sauce to penetrate deep into the crumb rather than pooling on the surface. Pour the warm sauce slowly and evenly over the hot cake, allowing each addition to be absorbed before pouring more. Use all of the sauce — it will seem like a lot, but the cake is designed to absorb it fully.
Allow the cake to cool completely in the pan before cutting — at least one hour, preferably two. As it cools, the sauce that has soaked in will set slightly, and the edges and bottom of the cake where the sauce has pooled will develop a lightly caramelized, almost sticky quality that is one of the best things about this recipe. The center of the cake will be supremely moist and tender, and the flavor of butter, vanilla, and buttermilk will be distributed throughout every bite.
Why the Buttermilk Sauce Makes This Cake
The technique of soaking a warm cake in a flavored sauce is not new — versions of it appear in Kentucky butter cake, poke cake recipes, and numerous Southern baking traditions. The principle is the same in all of them: a hot, freshly baked cake has an open, porous crumb structure that is ideally receptive to absorbing liquid. As the sauce soaks in and the cake cools, that liquid becomes part of the cake's structure rather than sitting on the surface, producing a level of moisture that cannot be achieved through the cake batter alone. The buttermilk in the sauce does double duty: its fat content adds richness that makes the cake taste richer than a plain butter cake, and its acidity provides a brightness that prevents the result from tasting cloying or one-dimensional. The vanilla in the sauce amplifies the vanilla already in the cake batter, doubling the intensity of the flavor in the most pleasant possible way.
Serving and Storage
This cake is excellent served at room temperature, directly from the pan, cut into generous squares. It needs no frosting, no additional garnish, and no accompaniment beyond a fork — though a dollop of softly whipped cream alongside a warm slice is a genuinely excellent option if you want to make it feel more like a dessert than a snack. It is also very good slightly warmed in the microwave, which softens the sauce-soaked crumb to something approaching molten without requiring any additional effort.
Store the finished cake covered at room temperature for up to three days — it actually improves over the first 24 hours as the sauce continues to meld with the crumb and the flavors deepen. After three days, cover and refrigerate for up to another three days; bring slices to room temperature before eating for the best texture. The cake also freezes well: cut into individual portions, wrap each tightly in plastic wrap, and freeze for up to two months. Thaw at room temperature or briefly in the microwave.
Tips for the Best Result
All ingredients should be at room temperature before you begin — cold butter will not cream properly, cold eggs can cause the batter to curdle, and cold milk added to a butter-based batter can cause the butter to seize. Take everything out of the refrigerator at least 30 to 45 minutes before you start mixing. Do not overmix the batter once the flour has been added — the moment the last streak of flour disappears is the moment to stop. Make the holes in the cake immediately when it comes out of the oven, while the crumb is at its most open and receptive, and pour the sauce immediately after making the holes so both are at peak temperature for maximum absorption. And allow the cake to cool fully before cutting — slicing into a hot cake that has been soaked in sauce will produce a messy, collapsing result rather than clean, beautiful squares.
