1. Pour sugar into a food processor fitted with a steel blade.
2. Zest the limes and put the zest in the processor with the sugar. Process until sugar and zest are very fine and fully incorporated.
3. Cream the butter in a mixer. Add the lime sugar mixture and mix until fully combined. Add the eggs one at a time, mix until fully incorporated. Then, add lime juice and mix again until the whole mixture comes together.
4. Pour mixture into a saucepan and place over medium heat. Stir mixture constantly over medium heat for about 10 minutes or until the curd thickens. Do not let it simmer or boil! The curd will come together quickly and be thick enough to coat the back of a spoon. Once it is complete, remove from heat and cool to room temperature. Mixture can be stored in the refrigerator for long periods of time.
5. To assemble, spoon the curd into the tart shells(s) and top with berries.
Yields 3 cups of filling. Enough for 16 individual 4” tarts, or one large 12” tart.

Ideas for using Citrus Curd: Filling for tarts, topping for Pavlova, topping for pound cake, layers in an English Trifle, layers in a Parfait, filling for Gingerbread muffins, filling for Profiteroles or other puff pastry treats.