Ceviche fronterizo with albacore tuna

Cut the tuna into pieces a little smaller than half an inch and finely chop the white onion.

Put the fish in a stainless steel or glass bowl, not one that could react with the acid, and put the onion on top.

Pour on enough fresh lime juice for the fish to float freely and mix in the onion.

Refrigerate 20 minutes for a rare ceviche, longer for more well done.

When the fish turns pale, tip off the lime juice, leaving a couple of tablespoons to season the dish; move to a bigger bowl.

Chop the green chili, cilantro and cherry tomatoes; add with the green olives and stir together.

Taste, then add salt until it balances the lime, stirring until dissolved; add sugar if wanted.

Stir in a couple of tablespoons of olive oil for creaminess and taste a final time.

For fancy tostadas, cut long triangles from a frying tortilla and fry, pushing them down in the oil to cup them.

Pile the ceviche onto tostadas or chips and serve fresh.