Make the crust: Preheat oven to 350 degrees. Whisk together cake flour, zest, and sugar in a medium bowl. Cut in the butter with a pastry cutter or two knives until the mixture resembles fine crumbs and starts to cling together. Press the mixture into the bottom (this step is a lot harder than it sounds, but be patient and use the back of a spoon to help spread/press the mixture down. I also stuck mine in the fridge for a bit to make the butter less sticky) and up the sides of a 10-inch cast iron skillet.Make the filling: Cream together the butter and sugar until fluffy and pale yellow (about 2-3 minutes). Mix in the egg until just combined. Alternate adding the flour and evaporated milk, mixing after each addition. Mix in the corn syrup, vanilla extract, lemon extract, and lemon zest. Pour the filling into the crust and sprinkle the top with icing sugar.Bake and assemble the cake: Bake for 30 to 40 minutes or until cake is nearly set (mine was probably ready around 35). Some jiggle is fine — do not overcook! It’ll finish setting up as it cools. Sprinkle some more powdered sugar on top. Let the cake cool in the skillet for 2 hours. In the meantime, beat heavy cream and 2 tablespoons powdered sugar together in a bowl to stiff peaks. Pile heaps of fresh blueberries into the center of your cooled, set gooey butter cake, top with a mountain of freshly whipped cream and lemon zest, and serve.