In a bowl, mix brown sugar, cumin, chili powder, salt, and pepper. Rub on the salmon. Cover the salmon and chill at least 30 minutes or up to four hours.
Lay salmon on a piece of aluminum foil. Heat the grill to high heat and lay the aluminum foil on the grill. Let the salmon cook until it just flakes apart and only a little pink is left, 15-20 minutes.
Divide the lettuce among four plates. Place a serving of salmon on each mound of greens, drizzle with the tomato vinaigrette, and sprinkle even with the cheese and green onions.
Tomato Vinaigrette: In a bowl, combine 1 cup of grated tomatoes, ¼ cup red wine vinegar, 2 Tablespoons olive oil, ½ teaspoon Dijon mustard, 1 Tablespoon minced shallot, and season with salt and pepper.