1Preheat the oven broiler. Line a baking sheet with aluminum foil. Place the salmon on the foil, and brush with 2 tablespoons melted butter. Season with salt and pepper. Broil 15 minutes, until fish is easily flaked with a fork.
2Melt the remaining butter in a skillet over medium heat, and saute the mushrooms until tender.
3Place the tomatoes in a bowl, and drizzle with 1 tablespoon olive oil. Season with salt and pepper.
4In a large bowl, toss together the salmon, mushrooms, tomatoes, lettuce, avocado, cilantro, and jalapeno. Drizzle with remaining olive oil and the vinegar. Season with salt and pepper, and sprinkle with feta cheese to serve.