In a medium saucepan over medium-high heat, melt sugar stirring constantly to prevent burning. Stir until melted sugar becomes a golden amber brown color - about 6-7 minutes.
Meanwhile, in a small saucepan, bring 1/4 cup water to a boil.
Once sugar is completely melted and amber colored, add boiling water to the melted sugar. Stir constantly. This will sizzle and bubble rapidly.
Add butter to melted sugar and water mixture. Once completely melted, remove from the heat.
Add heavy cream and stir until combined.
Mix in vanilla extract and pinch of salt (optional).
Pour into desired jar or container and let cool.
Serve warm or store in the refrigerator for up to 3 weeks.