Saute the leek and ajis in 1 tb. of the butter and the olive oil for 30 seconds. Add the Lima beans, water, and the citrus juice. Bring to a boil, then reduce the heat, cover and simmer for 8 to 10 minutes or until the beans are tender.
Mix the 1 tb of butter with the citrus zest and the salt and pepper. Drain the beans and add the butter mixture. Simmer for a minute and stir to coat the beans.