1. In a medium-size saucepan heat oil over medium heat; add onion and cook 5 minutes, stirring occasionally. Stir in quinoa, broth and 1/4 teaspoon of the salt. Bring to boil; reduce heat to medium-low and simmer, covered, for 17 to 18 minutes until liquid is absorbed and quinoa is tender. Stir in asparagus during last 5 minutes of cooking time. Add an additional 1/4 cup water if quinoa becomes too dry. Let stand, covered, 5 minutes.
2. Just before serving, stir Parmesan and butter into quinoa.
3. Meanwhile, heat a grill pan over medium-high heat; lightly grease. Season tuna with remaining 1/8 teaspoon salt, Italian seasoning and black pepper. Grill for 2 to 3 minutes per side for medium-rare.
4. Cut each piece of tuna into 2 servings and serve over quinoa risotto.