Place the quinoa and 2 cups of water in a medium saucepan. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes until the water is absorbed. Remove from heat and let it sit covered for 5 minutes. Fluff with a fork.
While the quinoa cooks, combine the diced avocados, halved cherry tomatoes, chopped red onion, cilantro, lime juice, 1 tablespoon of olive oil, and a pinch of salt in a mixing bowl. Stir gently to avoid mashing the avocados. Set the salsa aside.
Pat the salmon fillets dry with paper towels. Brush them lightly with the remaining tablespoon of olive oil and season both sides with salt and black pepper.
Heat a grill or grill pan over medium-high heat. Place the salmon skin-side down if using skin-on fillets and cook for 4 to 5 minutes per side until the fish flakes easily with a fork.
Divide the cooked quinoa among four plates. Top each portion with a grilled salmon fillet and a generous scoop of avocado salsa.