In a mixing bowl, zest and juice the limes, add coriander, garlic, chilli and chives and set aside.
In another bowl, add water and some ice. Throw in red onion - this will take the sharpness off, set aside
Place a frying pan over high heat and add a splash of oil. Pan-fry prawns or tuna on both sides until they change colour.
Add the prawns or the tuna to the bowl with the herby marinade. Leave them there for no longer than 2 minutes, as the prawns or tuna will start getting cured by the acidity of the lime
Grab a plate and spread a bit of the marinade on the bottom, top it with prawns or tuna and some iced onions, serve with a side of tostadas and esquites.