I have been working on a lemon poppyseed cake recipe and am thinking I finally have hit on the proper cake texture and lemon flavor. Since I am testing this recipe with the goal of using it for a stacked wedding cake, I need something with some decent structure, but I had gotten a specific request for a cake that was lighter and flufflier than pound cake (a classic spot for these flavors) and moister/denser than chiffon cake (my personal favorite). In my research, I found no recipes for lemon poppyseed cake that hit this middle ground, and many of the lemon cakes (to which I would throw in poppyseeds) turned out too moist and delicate to be used for a stacked cake.
After many test runs (and long-suffering tasters!), I am using the All-Occasion Downy Yellow Cake from Rose Levy Beranbaum's The Cake Bible (an slightly different version for a springform pan is published on Rose's site) and flavoring it with lemon oil, lemon zest and poppyseeds. As I discovered, you cannot just "throw in" some fresh lemon juice to a cake recipe and expect the crumb to be as soft, high or airy. Lemon juice is, of course, acidic, so it changes the chemical reaction and causes the cake to bake too quickly, leaving it cracked at the top and the texture low and dense.
But adding lemon oil, extract and/or zest will add flavor without ruining the structure*. I tested with Boyajian lemon oil by 1/8-teaspoons until I got the intensity I was looking for. Be very conservative with citrus oil or extract - it is far more potent than fresh juice. Also, these oils need to be kept in the fridge. I somehow missed that on the label of my first bottle, which had been sitting on a shelf over a year-- and the bitter cake that resulted was a good lesson.
Nothing is more painful than a baking project ruined by a 1/4 teaspoon of something.
But, nothing is more joyous than it coming out correctly after that!
Baking is histrionic.
Here is a 6" test cake (for the top tier) with a bunch of dots that make it look like a milkglass vase. The dots help disguise the uneven buttercream, which is more skillfully avoided by using a heavy duty turntable.
The raspberries on top hint at the raspberry cloud filling inside the cake: a small amount of butter cream mixed with a genrous portion of raspberry puree (with all the seeds strained!) into which I pressed a single layer of fresh raspberries.
The tart intensity of the raspberry filling was the perfect foil to the velvety, fluffy cake, punctuated by the little crunch of poppyseeds.
Of course, with such a delicate balance, the powdered sugar buttercream was not refined enough, so I will use a type of cooked sugar buttercream using meringue. Also known as European buttercream, it has far less sugar than the common American powdered sugar buttercream and won't overpower the cake I worked so hard to create. You can read a lovely explanation of and ode to meringue and its application to buttercream at the Occasional Baker.