In a small saucepan over medium heat, melt the butter. Once it’s fully melted, increase the heat to medium-high and whisk every 30 to 45 sec- onds to scrape up the milk solids, browning the butter more quickly. When the butter is golden brown and nutty-smelling, transfer it to a small heat- proof bowl. Be sure to scrape in the brown bits from the bottom of the pan, as they contain the most flavor.

Place the butter over an ice bath and whisk until slightly firm and creamy-looking but not fully hardened, about 5 to 10 minutes. It should have the texture of a softened stick of butter. Add the honey and vanilla and whisk to combine.

Preheat the oven to 350°F (175°C). Grease an 8-inch (20 cm) square baking pan and line it with parchment paper.

In a medium bowl, whisk together the flours, baking powder and salt; set aside.

In a stand mixer fitted with the whisk, whisk the brown sugar and eggs on medium for about 5 minutes, or until you reach the ribbon stage—if you lift the whisk up and move it around while letting the batter drizzle back into the bowl, it will create a silky elevated “ribbon” on the mixture’s surface. Add the brown butter mixture and sourdough discard, then mix for just 5 to 10 seconds; they should not be fully incorporated.

Reduce the speed to low and add the flour mixture. Mix for 15 seconds, then scrape down the sides and bottom of the bowl to incorporate any dry patches. Mix for 10 seconds. When the flour looks almost fully incorporated, add the pecans and mix just to combine.

Pour the batter into the prepared pan and use a palette knife or spatula to smooth the top.

Bake for 55 minutes, or until a cake tester inserted in the center comes out clean. Let cool in the pan for 5 to 10 minutes, then transfer the cake to a wire rack to cool completely before slicing into squares. Store in an airtight container at room temperature for up to 3 weeks.