Whether you decide to feed a high quality kibble or a commercially prepared whole foods diet, the following directions will apply.
Puppies between 8 and 16 weeks of age do quite well on 3 meals a day. They start out with about a large handful of kibble for each meal or about 1/4 cup. At about 4 to 6 months of age you may begin feeding your puppy twice a day, about 1/2 cup or so each time. Somewhere between 10 and 18 months of age you may begin feeding just once a day--with some really good eaters you may need to feed just once a day by 6 or 7 months of age.
Each time you feed your puppy, put the food down for approximately 15 minutes. If the puppy hasn't finished it after 15 minutes, pick it up and put it away until the next feeding time. Do NOT try to feed in between. Refrigerate if you are feeding a commercially prepared whole foods diet. Do not worry if your puppy appears thin. Puppies are just like humans. Some are very thin while growing up and some are not. It is highly unlikely your puppy will starve itself unless it is already ill. A puppy that grows slowly is best--there is no first prize for gaining full size as early as possible! Puppies who grow slowly are more likely to be able to develop muscle and tissue at the correct rate to keep up the the bone development. Of course some puppies are gluttons! Be careful not to overfeed a glutton.
As adults some Cavaliers may only eat 1/2 cup of food per day, others may eat as much as 1 full cup of food per day. I do not suggest feeding an adult Cavalier twice a day even though it is best for the dog. Cavaliers do not eat much! Half of very little is almost nothing! Nearly every owner I've known who tried to feed an adult twice a day ended up with an overweight Cavalier. When they try to divide 1/2 or 2/3 cup of kibble into two servings the amount barely covers the bottom of the pan--so they add just a little bit more so they don't feel as though they are starving their Cavalier. A little bit more every meal eventually ends up being a lot more! And their Cavalier becomes overweight. With one meal a day the amount looks to our eyes as though it is a half way decent amount and we are much less likely to add just a little bit more each day.