Why this recipe works: hailing from France’s Brittany coast, where butter is king, Gateau Breton is a simple yet stately cake, rich in flavor, with a dense yet tender crumb that falls somewhere between shortbread cookie and pound cake. Most recipes call for creaming the butter and sugar before incorporating egg yolks and flour, with some specifying upward of 10 minutes of creaming. But extended creaming incorporated too much air into the batter and resulted in a light, fluffy crumb – the opposite of what we wanted. Creaming the butter for a more reasonable 4 to 5 minutes (only 3 minutes of which was with the sugar) produced an ultra-thick batter that baked into a firm yet tender cake. Briefly freezing a layer of the batter in the cake pan made easy work of spreading on a bright apricot filling, and a second stint in the freezer firmed up the apricot-topped batter so we could cleanly apply the top layer. We strongly prefer the flavor of California apricots in the filling. Mediterranean or Turkish apricots can be used but increase the amount of lemon juice to 2 tablespoons. This cake is traditionally served plain with coffee or tea but can be dressed up with fresh berries, if desired.
1. For the filling: process water and apricots in blender until uniformly pureed, about 2 minutes. Transfer puree to 10-inch nonstick skillet and stir in sugar. Set skillet over medium heat cook, stirring frequently, until puree has darkened slightly and rubber spatula leaves distinct trail when dragged across bottom of skillet, 10 to 12 minutes. Transfer filling to bowl and stir in lemon juice. Refrigerate filling until cool to touch, about 15 minutes.
2. For the cake: adjust oven rack to lower-middle position and heat oven to 350 degrees. Grease 9-inch round cake pan.
3. Using stand mixer fitted with paddle, beat butter on medium-high speed until smooth and lightened in color, 1 to 2 minutes. Add sugar and continue to beat until pale and fluffy, about 3 minutes longer. Add 5 egg yolks, one at a time, and beat until combined. Scrape down bowl, add rum and vanilla, and mix until incorporated, about 1 minute. Reduce speed to low, add flour and salt, and mix until flour is just incorporated, about 30 seconds. Give batter final stir by hand.
4. Spoon half of batter into bottom of prepared pan. Using small offset spatula, spread batter into even layer. Freeze for 10 minutes. Spread ½ cup filling in even layer over chilled batter, leaving ¾ inch border around edge (reserve remaining filling for another use.) Freeze for 10 minutes.
5. Gently spread remaining batter over filling. Using offset spatula, carefully smooth top of batter. Brush with egg yolk wash. Using tines of fork, make light scores in surface of cake, spaced about 1 ½ inches apart, in diamond pattern, being careful not to score all the way to sides of pan. Bake until top is golden brown and edges of cake start to pull away from sides of pan, 45 to 50 minutes, rotating pan halfway through baking. Let cake cool in pan on wire rack for 30 minutes. Run thin knife around edge of pan, remove cake from pan, and let cool completely on rack, about 1 hour, before serving.
“Gateau Breton is a classic French butter cake. It’s a simple yet pretty cake, rich in butter, with a dense, tender crumb. I have to be honest, I was very intimidated by this recipe. I’m not a pastry chef so it always takes some Jedi mind tricks to get me feeling bold enough to tackle anything that must be baked but after the first time I made the cake properly, I was in love.
Making this cake requires a bit of patience because it has multiple levels: there’s the base of the cake, the delicious apricot jam in the middle, and then the top layer that has to be (and it is) firm enough to not taint the jam. There’s time in the freezer and then baking time; seemingly laborious but actually it’s a masterpiece. It’s the Sistine chapel of cakes, right down to its decorative top.”