Prepare a Dish: Grease an 8×8-inch dish or line it with parchment paper.
Mix Ingredients: In a large microwave-safe bowl, combine the butter, corn syrup, granulated sugar, brown sugar, and sweetened condensed milk. Stir well to combine.
Microwave: Microwave the mixture on high for 6 minutes, stopping every 2 minutes to stir. After 6 minutes, the caramel should be bubbly and thick.
Add Vanilla: Carefully remove the bowl from the microwave (it will be hot!) and stir in the vanilla extract. If you like a salty-sweet flavor, sprinkle some sea salt over the top.
Cool: Pour the caramel mixture into the prepared dish and let it cool for at least 30 minutes to 1 hour. Once cooled, cut into squares and enjoy!
