I've become a kumquat fan in recent years, and usually eat them raw. Things I've discovered/decided:
1. Avoid ones that have any hint of green on the rind. If you can't avoid them, trim off the green (it's usually closest to the stem).
2. Smaller is better. (By my logic, smaller fruits have a higher ratio of peel to pulp, so less sourness.)
3. If you find you've gotten a batch with many seeds, split in half and remove seeds.
4. To bring out the essential oils, roll the kumquat between your fingers to soften it & enhance the flavors.
I make a few batches of candied kumquat rinds last year. It's somewhat labor intensive for an end product that I could easily eat in one sitting, but worth it.
Kumquat Chips
4 cups whole kumquats
2 cups sugar
1 cup water
Make syrup with sugar and water. Wash fruit and slices an X on the stem end. Cover with water and bring to a boil. Drain and cool. Slit kumquats and take out pulp. Drop in boiling syrup and cook for 10 minutes. Cover, let stand over night. Cook again for 20 minutes. Lift with tongs and place on waxed paper to cool overnight or longer. Fill with pecan and roll in granulated sugar. Store in refrigerator.
Source:
http://www.kumquatgrowers.com/morerecipes.htmlAs an added bonus, the kumquat flavored simple syrup that's left over is a fantastic addition to a variety of drinks. However, you cannot reuse it to make a second batch of candied rinds.