Preheat oven to 375 degrees F. Coat a 9-inch pie plate with nonstick cooking spray and set aside. Cook pasta according to package directions. Use a slotted spoon to remove ravioli from cooking water and place on a tray lined with parchment paper to drain. Add coarsely chopped asparagus to cooking water for 1 minute. Drain and rinse with cold water. Set pasta and asparagus aside. In a medium saucepan cook garlic in butter over medium heat for 1 minute. Stir in flour until coated. Stir in milk all at once. Cook and stir until thickened and bubbly. Remove from heat. Stir in Parmesan cheese, tarragon, lemon peel, and salt.
To assemble, spread a small amount of lemon sauce in the bottom of the prepared pie plate. Arrange half of pasta over the sauce to cover bottom. Spoon half of the remaining sauce over ravioli. Arrange the asparagus over the sauce. Top with remaining ravioli and sauce.
Bake, uncovered for 20 to 25 minutes or until bubbly. Remove to a wire rack and cool 10 minutes before serving. Top with additional asparagus and lemon peel, if desired.