In a small sauce pan, whisk together brown sugar, coconut oil, fresh lime juice, vanilla and sea salt over medium-low heat until bubbly. Reduce heat and simmer until sauce thickens slightly (5 minutes). Remove from heat and set aside.
Place pineapple slices on a medium-high grill. Cook for 3-5 minutes (or when grill marks start to appear), flip and cook again for 3-5 minutes.
Remove from grill, drizzle with sauce, top with frozen dessert and enjoy :)