Grab a medium saucepan (not nonstick) and toss in your granulated sugar. Set it over medium heat and stir with a wooden spoon or silicone spatula. Those sugar clumps will soon vanish, leaving you with a rich amber liquid (about 6 minutes should do, but watch out to make sure it doesn't burn).
Add the unsalted butter. Give it a good stir until the butter is fully combined and melted (3 to 4 minutes). If you see any separation or clumps, take it off the heat and whisk until it's smooth again. Wear some gloves to keep splatter away.
Grab the heavy cream. Slowly pour it in while stirring constantly, then let it boil for a minute without stirring. You can also whip out a candy thermometer: when it's done, it should hit around 220°F (or 104°C).
Remove it from the heat and sprinkle in some salt. Give it a good mix, then let it cool down a bit. It will thicken into the final caramel sauce. Enjoy!