In a large suacepan, bring 1/2 inch of water to a boil. Add asparagus; cover and boil for 3 minutes. Drain and immediately place asparagus in ice water. Drain and pat dry. Transfer to a large bowl. Add the cheese, tomatoes, onion and basil.
To make Dressing:.
In a small bowl, whisk the oil, vinegar, garlic salt and mustard and pepper. Pour over salad; toss to coat. Drizzle with lemon juice. Chill until serving.