Grill the salmon (add salt and pepper and a squirt of lemon on each side) about 4 minutes on each side (depends on thickness). Place washed baby spinach on two plates.
In a mixing bowl, mix drained and washed black beans and corn. Add peeled and cubed avacado. Thinly slice onion (include green tops) and mix in with diced tomato. Mix together. In a small mixing bowl, mix olive oil, tarragon vinegar and spices together well. Add to salad mixture. Heap about 1 cup of the salad onto spinach, place salmon on mixture and top with a spoonful of the salad. Cut a slice of lemon and squirt it over the spinach.