Pina Colada Jar Cakes

1 (20 ounce) can unsweetened crushed pineapple
1 (4 ounce) stick plus 3 tablespoons unsalted butter, softened
3 1/2 cups packed light brown sugar
4 eggs
1/2 cup dark rum
3 1/3 cups flour
1 1/2 teaspoons baking powder
1 teaspoon baking soda
1 cup sweetened flaked coconut

Preheat oven to 325 degrees F.

Before starting batter, wash 8 (1-pint) wide-mouth canning jars with lids in hot, soapy water and let them drain, dry, and cool to room temperature. Generously grease insides of jars.

Drain crushed pineapple for about 10 minutes in a colander, reserving juice. Pur