Place finely diced red onion (1/2 onion) in a cup of gold water. Let sit while preparing the rest of the salsa.
Add passata (1 cup), garlic (1 clove), lime juice (1 lime), chopped coriander/cilantro leaves (1 bunch) to a bowl and stir. Add the rinsed red onion, salt, and pepper. Adjust for seasoning.