ridiculously easy butterscotch sauce

INGREDIENTS

• 1/4 cup (4 tablespoons, 2 ounces or 1/2 stick) unsalted butter
• 1/2 cup (about 109 grams) packed dark or light brown sugar (I used dark)
• 1/2 cup (118 ml) heavy cream
• 1/2 teaspoon (2 grams) flaky sea salt (or 1/4 teaspoon regular salt), plus more to taste
• 1 1/2 teaspoons (8 ml) vanilla extract, plus more to taste