Place 1 cup cane sugar and 1/4 cup cold water in a medium saucepan and stir just until the sugar is dissolved. Set the pan over medium-high heat and bring to a boil.

Once boiling, stop stirring. Let the syrup cook undisturbed until it turns a dark golden amber color, about 10–12 minutes. (A candy thermometer is optional: aim for about 230°F for a thicker but pourable sauce or about 225°F for a slightly thinner sauce.)

When the caramel reaches the desired color or temperature, remove the pan from the heat.

Slowly pour in the warm cream (½ cup, warmed briefly in the microwave) in a thin stream while whisking constantly. The mixture will bubble vigorously—use caution.

Return the pan to low heat and simmer, stirring, for 1–2 minutes until the sauce is smooth and slightly thickened.

Remove from heat and whisk in 4 tablespoons unsalted butter, 1 teaspoon vanilla extract, and a small pinch of salt until fully incorporated and smooth.

Let the caramel cool slightly, then serve warm or transfer to a container and store in the refrigerator. To use again, reheat briefly in the microwave until pourable.