In a medium bowl, toss the apples with the lemon juice, brown sugar, cinnamon, nutmeg, and salt. Melt the butter in a medium skillet over medium-high heat. Add the apple mixture and cook until apples are saucy and softened, about 5 minutes. Carefully add the rum and cook another minute.
Divide ice cream among 4 bowls and top with hot apples.
Recipe courtesy of Rachael Ray