Prepare campfire: Heat coals until they are very hot, or let a campfire burn down until the wood is smoldering but without active flames.Line the Dutch oven with a parchment paper liner (to prevent the couscous from sticking to the pot). Sprinkle the salmon fillets with a pinch of the salt and set aside.Add couscous, broth, capers, oil, Italian seasoning and remaining salt to the Dutch oven. Stir to combine.
Add the tomatoes and green beans on top of the couscous mixture.Nestle the salmon fillets into the veggies and couscous. Set the lemon slices on top of the salmon.
Cover oven and place on coals. Cook about 20 minutes, or until the salmon easily flakes apart with a fork.Remove from heat and serve immediately.