My favorite Kalamansi!
Calamansi (Citrus × microcarpa), also known as calamondin, Philippine lime, or Philippine lemon, is an economically important citrus hybrid predominantly cultivated in the Philippines. It is native to the Philippines, Borneo, Sumatra, and Sulawesi in Indonesia in Southeast Asia, as well as southern China and Taiwan in East Asia. Calamansi is ubiquitous in traditional Filipino cuisine. It is naturally very sour and is used in various condiments, beverages, dishes, marinades, and preserves. Calamansi is also used as an ingredient in Malaysian and Indonesian cuisines.
Calamansi is a hybrid between kumquat (formerly considered as belonging to a separate genus Fortunella) and another species of Citrus (in this case probably the mandarin orange).