The best way to feed tomatoes is "little and often".
Professional growers feed at every watering so that plants have access to the minerals and nutrients they need 24/7.
Although this is not really practical for most people who grow tomatoes, plants respond well if the "little and often" principle is followed.
Firstly, it is best not to feed tomato plants (with tomato food) until the first pea-like fruit appear. Whenever plants are put into new soil or compost they are also receiving a new supply of food. If you feed them at this stage, you are feeding them twice.
Of course every experienced gardener has his or her own way of doing things and if you get the results ... there's no reason to change.
However, my method is to feed half the recommended amount at every other watering when the first fruit are at pea size.
When the fruit start to ripen I feed them half the recommended amount 2 out of 3 waterings, then when the second truss is ripening (or several ripe fruit on a bush variety) I feed at full strength every other watering.
This is of course time consuming and if you follow the directions on the tomato food container I'm sure that will be good too!
As plants become more mature , at their fruiting stage, so they need more food because to produce and ripen lots of fruit takes lots of energy.
The more fruit .... the more feed they need but don't be too generous with food because too much can damage roots on younger plants, and too much of one mineral can prevent other nutrients from being absorbed.
Large fruit varieties show crinkly skins as they grow ...
a bit like a garment that you'll grow into!