To blanch asparagus, heat 4 quarts water (add 1 tablespoon salt, if desired) in 6-quart Dutch oven to boiling. Add asparagus; cook 3 to 4 minutes or until asparagus is crisp-tender. Remove asparagus, and immediately immerse in bowl of ice cold water. Let stand 5 minutes. Drain well; pat dry with paper towels.
Place asparagus spears in ungreased 13×9-inch (3-quart) baking dish.
In medium bowl, mix Boursin™ cheese and whipping cream with whisk or fork until blended. Stir in Parmesan cheese; spread over asparagus. Top with tomatoes.
Bake 15 to 20 minutes or until heated through. Sprinkle with thyme.