This expression means; To be blind to something that is right in front of you.

In Spain the tomato was considered the “fruit of sin” until the late
Middle Ages. Traitors and thieves were often punished and publicly
humiliated, as they were made to walk around the streets for weeks
with “Tomates en los ojos” (tomatoes on the eyes). This would
make other villagers aware of their crimes, and was also intended to
make the criminals walk into things and endure mishaps as a kind of
retribution.
They saying “to have tomatoes on one’s eyes” is still used today in
many European countries when people fail to see something
obvious.