Step 1

In the bowl of an electric mixer, whisk together the yeast and milk. Set aside for a couple of minutes. Whisk in the melted butter, sugar, eggs, vanilla, and lemon zest. Add the flour and salt. Fit the bowl onto the mixer along with the paddle attachment. Mix on medium speed for 3 to 4 minutes, or until shiny. It will be a very loose dough-batter hybrid. Stop the mixer and scrape down the bowl well about halfway through the mixing time.

Step 2

Spray a medium bowl with cooking spray or oil it lightly. Scrape the dough into the bowl and dust the surface of the dough with a couple of teaspoons of flour. Cover the bowl tightly with plastic wrap. Let rise in a warm place until doubled in bulk, 45 minutes to 1 hour.

Step 3

Position a rack to the center of the oven and preheat it to 325°F. Spray a 9x13-inch glass baking dish with cooking spray.

Step 4

Flour your hands, transfer the dough to the baking dish, and pat dough into an even layer. Cover with plastic wrap and let rise a second time for 20 minutes. Meanwhile, prepare the topping.

Step 5

In the bowl of an electric mixer fitted with the paddle attachment, beat together the butter and cream cheese on medium-high speed until smooth and creamy. Add the granulated and brown sugars, vanilla, and salt, and beat until light and fluffy, about 3 minutes. Add the corn syrup and egg and beat until smooth. Reduce the mixer speed to low and gradually beat in the flour. Fold the batter by hand a few times with a large flexible spatula until well blended.

Step 6

When the dough has finished its second rise, dollop the topping over the dough. Use a small offset spatula to spread it evenly.

Step 7

Bake until puffed and golden, but still quite loose in the center, about 40 minutes (it will appear almost liquid under the surface in spots, but will quickly set upon cooling. Have a peek at the bottom of the cake through the glass dish; if it’s deeply golden, you’re in good shape). Let cool completely in the pan set on a wire rack. Dust with powdered sugar before slicing and serving.