Fudgy, decadent brownies swirled with gooey caramel sauce.
In a medium heavy-bottomed saucepan (large enough to coat the surface with an even thin layer of sugar), heat water and sugar over medium heat.* Make sure all of the sugar is evenly moistened from the water and there are no dry spots. It’s important to not stir the mixture, and instead gently swirl and shake the pan occasionally so the caramel will cook evenly and won't burn. The caramel will usually start to brown at the edges first. In that case, push the liquefied sugar towards the middle of the pan using a heatproof utensil such as a whisk, spatula, or wooden spoon.
*Note on making caramel sauce: Sugar can crystallize easily when heated. To prevent this, you can add a few drops of lemon juice to the sugar-water mixture. It won’t add lemon flavor, but it will prevent your sugar from becoming a giant crystal