Question

it is very commom in headlines to omit verbs principally the verb be . in rio de janeiros slums becoming brazil tourist hotspot , which verb is omitted

Answer 1

The verb to be was omitted, as yourself had already raised. It would be the same as "In Rio de Janeiro slums are becoming..."

Answer 2

O verbo é "are". A frase deveria estar assim:
In Rio de Janeiro, slums are becoming Brazil tourist hotspot.
Espero ter ajudado!