Grease a 9x13-inch baking pan with nonstick spray and flour. Set aside.
Add the yeast and warm milk to a bowl let it rest for a few minutes until foamy.
1 teaspoon instant yeast, ½ cup milk
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar together until fluffy, about 2 minutes.
8 tablespoons unsalted butter, ¼ cup granulated sugar
Add in the eggs, egg yolk, vanilla extract, and salt and beat until combined, about 1 minute
2 large eggs, 1 egg yolk, 1 teaspoon pure vanilla extract, ½ teaspoon kosher salt
Add in half of the flour, and beat until incorporated. Then, add in the milk mixture and beat until incorporated. Add in the remaining flour, and continue beating on low speed until the dough becomes stretchy, about 5-6 minutes.
2 cups all-purpose flour
Transfer the dough the prepared baking pan and use a spatula to spread it into an even layer.
Cover the pan with a towel and set in a warm place to rise for 1-2 hours.
Preheat the oven to 325°F.
To prepare the filling, add the butter, sugar, corn syrup, and salt to the bowl of a stand mixer fitted with the paddle attachment. Beat until combined, about 1-2 minutes.
10 tablespoons unsalted butter, 1¼ cup granulated sugar, ¼ cup light corn syrup, ¼ teaspoon kosher salt
Add in the egg, vanilla extract, and almond extract and beat until incorporated.
1 large egg, 1 teaspoon pure vanilla extract, ¼ teaspoon almond extract
Add in the flour and milk, little by little, beating until well-combined.
1 cup all-purpose flour, ¼ cup milk
Drop dollops of filling over the dough layer. Use a spatula to gently spread it in an even layer over the dough.
Bake for 30-35 minutes until golden brown and the center of the cake is mostly set, but still a bit jiggly.
Dust the cake with powdered sugar.
¼ cup powdered sugar
Let the cake rest for a few minutes before slicing into squares and serving. Let cool completely for cleaner slices. Parts of the cake may sink and form little craters, which is totally fine!