1. Using a sharp knife, cut segments from 1 1/2 grapefruits, cutting on either side of membranes. Place segments in a large bowl and set aside. Over a 2-cup measure, squeeze remaining half of grapefruit and leftover membranes. (You will need 1/3 cup; if needed, add white wine vinegar to equal that amount.) Whisk in honey, salt, pepper and oil until blended.
2. Preheat grill or large skillet over medium-high heat and coat with olive oil spray. Grill asparagus for 8-10 minutes, turning occasionally until tender crisp. Set on board to cool slightly. Cut asparagus in half, crosswise and add to the large bowl.
3. Whisk dressing and add half to the large bowl. Gently toss to combine and place on serving platter. Top with hazelnuts and Le Rustique cheese; serve with remaining dressing on the side.