Lightly grease a 8" x 8” and line with foil or parchment paper.
In a medium-sized microwaveable bowl, stir together all ingredients to combine (some larger pieces of butter are fine).
Cook in microwave six minutes on high, stopping to stir after every two minutes. After six minutes, check the temperature with a candy thermometer, and if it’s below 245°F (118°C) continue cooking in thirty second intervals until 245°F (118°C) is reached. If no thermometer is available a teaspoon of caramel can be dropped into a glass of cold water and should form a soft, pliable ball.
Carefully pour caramel into lined dish and sprinkle with flaky salt, if desired. Let cool at room temperature for at least two hours.
When cooled, release caramels from pan and cut into desired size and wrap in wax or parchment paper. Caramels can be stored at room temperature in an airtight container for up to one week.