Decent ethnic meals in Tortosa? Not until local people gets interested in their new neighbours way of life.
You had a Paki/Hindu restaurant in Remolins, now closed because only Pakistanis and Hindus ate in.
You have a russian/catalan restaurant in front of the train station. Catalans go for drinking and eating local. Russians and Ukranians go for eating (But I guess most of them go for the "Baltika" beer)
Chinese restaurants mainly sell "Arroz 3 delicias" 'cause is the dish which is more likely to paella.
Most of the kebabs are crap.
The only one who is getting well, to my surprise, is the Moroccan restaurant in Montserrat square (where the mosque is) even though most of the people you'll see there go just for the mint tea.

The problem of Tortosa is that people who is interested in discovering ethnic meals do not leave in Tortosa anymore. Such a pity