Step 1

Heat the oven to 350ºF.

Step 2

Melt 1 1/2 sticks cut-up unsalted butter in a medium, light-colored skillet or saucepan over medium heat. Cook, stirring and scraping the bottom occasionally, until it begins to bubble and pop. Continue cooking until it foams, smells nutty, and the solids turn dark brown, 8 to 10 minutes.

Step 3

Scrape into a small heatproof bowl and stir in 3/4 teaspoon kosher salt. Set aside to cool slightly while you prepare the remaining ingredients.

Step 4

Line an 8x8-inch baking pan with 2 sheets of parchment paper, positioning them perpendicular to each other so that the parchment hangs about 2 inches over all sides of the pan to form a sling.

Step 5

Whisk 2 cups all-purpose flour, 1/3 cup granulated sugar, 1/3 cup packed light brown sugar, and 3/4 teaspoon baking powder together in a large bowl.

Step 6

While stirring with a flexible spatula, slowly pour the browned butter into the flour mixture and stir until a crumbly dough forms.

Step 7

Reserve 3/4 cup of the dough for topping. Transfer the remaining dough to the baking pan and press it into an even layer with your hands or the bottom of a measuring cup (reserve the bowl).

Step 8

Bake until lightly golden brown and the top appears dry, about 15 minutes. (This is a good time to cut the apples.) Place on a wire rack.

Step 9

Increase the oven temperature to 375ºF. Whisk 2 large eggs in the reserved bowl (no need to clean) until lightly beaten. Whisk in 1/3 cup granulated sugar, 1/3 cup packed light brown sugar, 2 tablespoons all-purpose flour, 2 tablespoons heavy cream, 1 teaspoon apple pie spice, and 1/4 teaspoon kosher salt.

Step 10

Add 1 1/4 pounds peeled and sliced apples, and toss to coat. Transfer onto the hot crust and arrange into an even layer. Crumble the reserved dough evenly over the filling.

Step 11

Bake until the topping is golden brown, the apples are tender, and the filling is thickened to a jam consistency, 55 to 60 minutes.

Step 12

Let cool completely in the pan, about 2 hours. Grasping the excess parchment, lift the slab out of the pan and place on a cutting board. Cut into 12 or 16 pieces.