Cut the Norwegian salmon into cubes, then place in a medium stainless steel or glass mixing bowl with thinly sliced onion, lime juice, and lemon juice. Stir to mix well, then cover with plastic wrap and refrigerate.
Add chopped jalapeño, diced avocados, chopped tomatoes, finely chopped cilantro, Kosher salt, and freshly ground black pepper. Stir well, then taste and adjust seasoning as needed.
If using, make homemade tostadas or serve immediately with tortilla chips.
Before serving, toss with jalapeño, chopped tomatoes, avocado, and fresh cilantro.