1. Preheat your oven to 325°F (165°C). Line a baking sheet with parchment paper.

2. In a large, clean, and dry bowl, beat the egg whites with an electric mixer on medium speed until they start to become frothy.

3. Gradually add the 1 cup of sugar, 1 tablespoon at a time, while continuing to beat the egg whites. Once all the sugar has been added, increase the speed to high and beat until stiff, glossy peaks form.

4. Gently fold in the cream of tartar and 1/4 teaspoon of salt.

5. Spoon the meringue mixture onto the prepared baking sheet, creating 6 equal-sized mounds.

6. Bake for 25-30 minutes, until the meringues are lightly golden and crisp on the outside.

7. While the meringues are baking, make the salted caramel sauce. In a medium saucepan, combine the 1/2 cup of sugar and 2 tablespoons of water. Cook over medium-high heat, swirling the pan occasionally, until the sugar has dissolved and the mixture turns a deep amber color, about 5-7 minutes.

8. Remove the saucepan from the heat and carefully pour in the heavy cream (the mixture will bubble up). Whisk until the caramel is smooth and combined.

9. Return the saucepan to low heat and add the unsalted butter, whisking until melted and fully incorporated.

10. Remove the salted caramel sauce from the heat and stir in the 1/4 teaspoon of flaky sea salt.

11. Allow the meringues and caramel sauce to cool slightly, then drizzle the warm caramel over the top of the meringues.

12. Serve the Salted Caramel Swiss Meringue immediately, or refrigerate until ready to serve.