Cheesy Baked Quinoa and Cauliflower

Name: Cheesy Baked Quinoa and Cauliflower
Ingredients: 1 cup quinoa; 1 head cauliflower, cut into florets; 5 tablespoons olive oil, divided; 1 ½ teaspoons kosher salt, divided; Freshly ground black pepper; 4 tablespoons (½ stick) unsalted butter; 1 yellow onion, finely chopped; 4 tablespoons all-purpose flour; 4 cups whole milk; 4 ounces sharp white Cheddar cheese, grated (1 cup), divided; 4 ounces fontina cheese, grated (1 cup), divided; 2 ounces Parmesan cheese, finely grated (1 cup), divided; 2 cups panko; 1 tablespoon fresh thyme leaves