Step 1

Preheat oven to 350°F. Melt butter in a medium saucepan over medium. Cook, whisking constantly, until butter browns and smells nutty, 5 to 7 minutes. Immediately pour into a bowl. Place in refrigerator to cool, whisking every 5 minutes until thickened and creamy, about 20 minutes. (Butter should look like melted peanut butter.)

Step 2

Beat eggs and sugar with an electric mixer on medium speed until thickened and pale yellow, about 3 minutes. Whisk together flour, baking powder, and salt in a bowl. Add to egg mixture in thirds, alternately with cooled butter, beginning and ending with flour mixture, beating on low after each addition. Slowly beat in maple syrup; add vanilla, and beat just until combined. Fold in 1 cup of the pecans with a spoon.

Step 3

Pour batter into a greased and floured 13- x 9-inch baking pan, and spread into an even layer. Sprinkle with remaining 1⁄4 cup pecans.

Step 4

Bake in preheated oven until golden and a wooden pick inserted in middle comes out clean, about 35 minutes. Transfer pan to a wire rack to cool completely, about 1 hour. Cut into 24 bars.