Preheat oven to 350°F (177ºC). Line two baking sheets with parchment paper or silicone baking mats.
In a large bowl, combine egg whites, sugar, salt, and rum. Beat with a whisk until mixture turns becomes foamy and begins to stiffen, and the sugar is mostly dissolved. You may use a mixer if you'd prefer-- whisk at least 2 minutes. Fold in flaked coconut and pineapple. Stir gently so the egg whites keep their shape.
Using a cookie scoop (I use this #50 cookie scoop for all of my standard size cookies), place a mound of cookie dough onto the baking sheet. Bake for 20 minutes or until golden brown, rotating the baking sheet ¼ of a turn halfway through baking time. Macaroons stay fresh in an airtight container up to 3 days at room temperature or 5 days in the refrigerator. Macaroons freeze well, up to 2 months. Thaw overnight in refrigerator.
Notes
*Crushed pineapple: drain this very well. I let mine sit in a mesh sieve for awhile and then pressed out the remaining liquid with a cloth kitchen towel.
All nutritional values are approximate and provided to the reader as a courtesy. Changing ingredients and/or quantities will alter the estimated nutritional calculations.