Preheat oven to 425°F. Lightly oil a baking sheet.
In a medium saucepan, combine quinoa, ¼ teaspoon salt, and 1 cup water. Bring to a boil, reduce the heat to simmer, cover, and cook until tender, about 12 minutes. Remove from the heat and let stand for 5 minutes.
Place salmon fillets skin-side down on prepared baking sheet. Rub with chili powder and ¼ teaspoon salt. Roast until opaque and flaky, about 10 minutes.
While salmon roasts, in a medium bowl combine avocado, 1 cup diced cucumber, jalapeño, green onion, parsley, lemon juice, and remaining ¼ teaspoon salt.
To serve, divide quinoa between serving bowls or plates. Top with salmon, then garnish with avocado relish.