Combine quinoa and water in a medium pot. Bring to a boil, cover, reduce the heat, and simmer for 15 minutes.
Remove from the heat and let it sit, covered for 10 more minutes. Fluff with a fork.
Bring 4 qrts water and 2 tbsp of kosher salt to a boil in a large pot. Prepare an ice bath by filling a large bowl halfway with ice, then add enough water so the bowl is 2/3 full.
Break corn in half then add to boiling water and cook for 2 minutes. Remove corn with tongs or strainer and plunge immediately into an ice bath.
Towel dry corn, cut kernels off cob, and place kernels in a large bowl.
Add quinoa, diced cucumber, avocado, basil, scallion and feta to the bowl. Add 1/2 cup of dressing to bowl and toss gently.
Season salad to taste with Kosher salt and black pepper, adding more dressing if desired. Top with sunflower seeds.