In a pan on the stove, heat sugar and water just until sugar melts.

Remove from heat and add 1 1/2 teaspoons citric acid. Stir until dissolved.

Let mixture cool for a few minutes and add rum extract, lime juice and food coloring.

Taste, and add more citric acid powder as needed, a 1/2 teaspoon at a time. The citric acid will be what gives this recipe it's tartness. The amount you will need will vary based also on the tartness of your limes. Mine weren't very tart at all, and I ended up using another 4 teaspoons to get it to where I was happy about the flavor.

Refrigerate until chilled.

Move and an ice cream maker. Churn in machine for about 55 minutes or until yours says it's ready (mine shuts off on it's own)..

Move to the freezer for a few hours before serving.

Makes about 8 cups