1. Preheat your oven to 350°F (175°C) and line a 9×13-inch baking pan with parchment paper, leaving some overhang on the sides for easy removal.
2. In a medium saucepan, melt the butter over medium heat. Continue cooking, swirling the pan occasionally, until the butter turns golden brown and smells nutty—about 5 to 7 minutes. Be careful not to burn it. Pour the brown butter into a heatproof bowl and let it cool slightly.
3. Once the brown butter has cooled but is still liquid, whisk in the granulated sugar and maple syrup until combined.
4. Add the eggs one at a time, whisking well after each addition. Stir in the vanilla extract.
5. In a separate bowl, sift together the flour, baking soda, salt, cinnamon, and cream of tartar (if using).
6. Gradually fold the dry ingredients into the wet ingredients using a spatula or wooden spoon until just combined. Avoid overmixing to keep the bars tender.
7. Pour the batter into the prepared pan and smooth the top with a spatula.
8. Mix the remaining 2 tablespoons of sugar with 1 teaspoon of cinnamon and sprinkle evenly over the batter.
9. Bake for 25-30 minutes or until the edges are golden and a toothpick inserted into the center comes out with just a few moist crumbs.
10. Allow the bars to cool completely in the pan on a wire rack. Once cool, use the parchment paper overhang to lift them out and cut into 12 squares.

I always find that letting these bars cool fully is key—they firm up nicely and the flavors meld beautifully. This patience reminds me of those slower cooking moments with my family, where waiting made the reward all the sweeter.