These zucchini pecan bars are tender, warmly spiced dessert squares made with shredded zucchini, chopped pecans, and a rich caramel-style frosting. The bars bake into a soft, lightly dense crumb, while the frosting sets into a smooth, sweet topping that complements the cinnamon and nutmeg.
Preheat the oven to 350°F. Grease a 9×9-inch baking pan with butter, then line it with parchment paper to help lift the baked bars out easily.
In a large mixing bowl, add the eggs, melted unsalted butter, granulated sugar, brown sugar, salt, cinnamon, nutmeg, and vanilla extract. Whisk thoroughly until the mixture is evenly combined.
Add the baking soda and whisk it into the wet mixture. Fold in the all-purpose flour until the batter is fully blended and no visible dry streaks remain.
Gently incorporate the shredded zucchini and chopped pecans, folding just until they are distributed throughout the batter.
Transfer the batter to the prepared baking pan and spread it into an even layer. Bake for approximately 35 to 45 minutes, or until the bars have risen and are baked through.
Let the baked bars cool slightly while preparing the frosting. The frosting is easier to spread when poured over the bars while they are still somewhat warm.
For the frosting, place the butter, brown sugar, milk or cream, and salt in a small saucepan. Warm the mixture over medium heat and bring it to a boil. As soon as it begins boiling, remove the pan from the heat.
Whisk in the powdered sugar until the frosting becomes smooth. Pour it over the warm bars and spread it promptly, as the frosting starts to firm up very quickly.
Allow the frosted bars to cool before cutting them into squares.