Prep Time 15 minutes mins
Cook Time 22 minutes mins
Resting Time 30 minutes mins
Total Time 1 hour hr 7 minutes mins
For the chewiest texture, avoid overbaking—pull the bars when the center still looks slightly soft and the tester has moist crumbs, not dry. Room-temperature eggs and buttermilk help the batter emulsify and stay tender, while vinegar boosts the red hue and reacts with cocoa for subtle tang. Natural cocoa keeps the color vibrant, but you can use Dutch-process for a deeper chocolate flavor (reduce vinegar to 1/2 teaspoon). If skipping the cream cheese swirl, sprinkle flaky salt or extra chips on top before baking for contrast. Bars store airtight at room temperature for 2 days or refrigerated up to 5 days, and they freeze well for 2 months; thaw wrapped at room temperature.