Seviche

1 . Stage

Add sliced onions to a saucepan over medium heat and add just enough water to cover. Bring to a simmer and cook just enough to soften. Remove from heat and drain. Rinse with cold water and drain.

2 . Stage

Score tomato with an X, skin deep, on the top and bottom. Place in the same saucepan used for the onions and add enough water to cover. Bring to a simmer and cook until soft and the skin starts to peel, about 5 minutes. Remove tomato and rinse under cold water until cool enough to hold in your hand. Using your fingers or the blade of a knife, gently peel off the skin. Place peeled tomato in a blender and purée.

3 . Stage

Combine onions, lemon juice, and olive oil in a large glass dish or bowl. Stir in oysters, puréed tomato, diced tomato, green onions, ketchup, and soy sauce. Season with parsley, garlic salt, sugar, and salt to taste.

4 . Stage

Chill before serving.