The salmon is pan roasted, making for easy clean-up. While the flavor of wild salmon is superior, a less expensive alternative is farm-raised salmon. The trade winds of Spain led directly to Vera Cruz, where the native people incorporated European ingredients such as olives, capers and other foods into their cuisine, giving it a European flavor.
Preheat the grill or broiler.
Toss the asparagus spears with 3 tablespoons of virgin olive oil and salt and pepper. Grill until just tender, about 3-4 minutes, rolling periodically. Set aside and keep warm.
Meanwhile, rinse and spin dry the watercress. Set aside.
Heat 3 tablespoons of the olive oil in a large sauté pan or skillet over medium-high heat.
Sprinkle the salmon with salt and pepper. Place it in the pan flesh side down, and sear until brown, about 2–3 minutes. Flip the salmon over.
Add the bell peppers, garlic, onions, tomatoes and wine to the pan; bring to a simmer. Cook, uncovered, until the salmon is medium rare, about 4-5 minutes.
Add the olives and butter, swirling the butter constantly until it is incorporated; check the seasonings and add more salt and pepper to taste.
Toss the watercress with extra-virgin olive oil and salt.
To serve, place 3 spears of asparagus on each plate. Top with a piece of salmon and one-quarter of the sauce, spreading it out evenly. Add one-quarter of the watercress to each plate.