1 cup (220 grams) firmly packed light brown sugar1¼ cups (283 grams) unsalted butter, melted, slightly cooled, and divided3 large eggs (150 grams), divided1 large egg yolk (19 grams), room temperature1 tablespoon (13 grams) plus 1 teaspoon (4 grams) vanilla extract, divided2 cups (250 grams) all-purpose flour⅔ cup (75 grams) finely chopped toasted pecans2 teaspoons (10 grams) baking powder1 teaspoon (3 grams) kosher salt1 (8-ounce) package (226 grams) cream cheese, softened1½ cups (180 grams) confectioners’ sugarButter Pecan Sauce (recipe follows)
Preheat oven to 350°F (180°C). Spray a 13×9-inch baking pan with baking spray with flour. Line pan with parchment paper, letting excess extend over sides of pan.
In a large bowl, whisk together brown sugar and ¾ cup (170 grams) melted butter until light and fluffy, 2 to 3 minutes. Whisk in 1 egg (50 grams) and egg yolk until smooth. Whisk in 1 tablespoon (13 grams) vanilla.
In a medium bowl, whisk together flour, pecans, baking powder, and salt. Using a rubber spatula, fold flour mixture into sugar mixture. Pour batter into prepared pan, smoothing top with an offset spatula.
In another large bowl, whisk together cream cheese, remaining ½ cup (113 grams) melted butter, remaining 2 eggs (100 grams), and remaining 1 teaspoon (4 grams) vanilla until well combined. Add confectioners’ sugar, beating until smooth. Spread onto crust mixture.
Bake until edges are golden brown and center jiggles slightly, 25 to 30 minutes. Let cool completely in pan on a wire rack.
Using excess parchment as handles, remove from pan, and cut into bars. Serve with Butter Pecan Sauce. Refrigerate in an airtight container for up to 3 days.