Preheat your oven to 400°F. Line a baking sheet with parchment paper.
In a small bowl, whisk together lime juice, cilantro, garlic, cumin, olive oil, salt, and pepper.
Place the salmon fillets on the prepared baking sheet and pour the marinade over them, ensuring they are well coated. Let them marinate for about 15 minutes.
Bake the salmon in the preheated oven for 12-15 minutes, or until it flakes easily with a fork.
While the salmon is baking, prepare the avocado salsa. In a medium bowl, combine diced avocado, tomato, red onion, lime juice, and salt. Gently mix until well combined.
Once the salmon is done, remove it from the oven and let it rest for a few minutes. Serve the salmon topped with the avocado salsa.