Position rack in upper third of oven; preheat broiler to high.
Place salmon on a rimmed baking sheet. Drizzle with 1 tablespoon oil and sprinkle with 1/2 teaspoon salt, 1/4 teaspoon pepper and cumin. Broil the salmon until it is opaque and flakes easily with a fork, 6 to 9 minutes.
Meanwhile, combine tomatillos, tomato, cilantro, onion, jalapeño and lime juice with the remaining 1 tablespoon oil and 1/4 teaspoon each salt and pepper in a medium bowl. Serve the salmon with the salad.
Tip: Although you'll want to remove the husk (and rinse off the sticky coating) before eating, look for firm tomatillos with an intact husk that's tight to the fruit.