Meyer Lemon Cornmeal Upside-Down Cake

The polenta cake from pastry chef Hannah Boyer of A16 Rockridge in Auckland served as a model for making this dense, moist dessert. When sliced lemons are baked under the crust and soaked in butter and brown sugar, they take on a marmalade-like flavor. Before taking the cake out of the oven, make sure that it is completely baked (see Step 6), otherwise it may fall through.
Preheat the oven to 350 degrees. Spray the inside of the 9-inch-diameter mold with a spray of vegetable oil. Line the mold tightly with a 12-inch diameter mold. lay out a circle of parchment paper*, pressing down the creases. Drizzle the parchment with oil; set aside.In a small saucepan over medium heat, bring 1/4 cup butter and brown sugar to a boil, stirring constantly. Pour into a lined pan and spread evenly.Thinly slice 2 lemons crosswise, using a hand slicer and removing the seeds with the tip of a knife as you go. Discard the tips. Place a small slice of lemon in the center of the oil mixture in the skillet. Arrange a few more slices in overlapping circles to fill the shape (each slice should overlap the previous one by half). Save the extra lemon for other uses.Beat the remaining 1/2 cup butter, granulated sugar, and lemon zest in a large bowl with a mixer on medium speed, then on high, until the mixture is pale and fluffy, 3-4 minutes. Add 1 egg at a time, scraping off the inside of the bowl and beating well on high speed, about 1 minute per egg. In a medium bowl, whisk together the flour, cornmeal, baking powder, and salt. Mix the milk and vanilla together.Add a third of the flour mixture to the butter mixture and beat on low speed; whisk inside the bowl. Mix with half of the milk mixture. Repeat to combine the remaining ingredients, finishing with the flour mixture. Pour the batter onto the pan; spread evenly.Bake until the cake comes out of the center with light pressure, 50 to 55 minutes (it is well browned). Let cool in the pan on a wire rack for at least 2 hours. Run a thin knife between the parchment and the mold; release the edges. Flip the pie onto a plate. Remove the parchment and cut the cake with a notched knife.* Circle 12 inches in pencil to get a smooth circle. place on parchment.Cooking time: up to 1 day.