In a medium saucepan over medium heat, melt the unsalted butter until it begins to foam.

Sprinkle the granulated sugar substitute into the melted butter and stir constantly until completely dissolved.

Continue cooking, stirring, until mixture turns a light amber color and begins to bubble vigorously.

Carefully add the heavy cream, whisking continuously to combine into the caramel base.

Stir in sugar-free maple syrup if desired, then reduce heat to low.

Simmer gently while stirring for a couple of minutes until the sauce thickens and becomes glossy.

Remove saucepan from heat and whisk in vanilla extract and salt until smooth.

Let the caramel cool slightly; it will thicken further as it cools.

Transfer to a jar or heat-proof container to store or use immediately.