Gluten Free Asparagus-Tuna Casserole

Preheat oven to 375°F. In a large saucepan cook pasta according to package directions, adding potatoes for the last 4 minutes of cooking; drain.

Meanwhile, in a large Dutch oven heat 2 tablespoons of the butter over medium heat. Add onion; cook about 3 minutes or until tender, stirring occasionally. Stir in flour, salt, and pepper; cook and stir for 2 minutes. Gradually stir in milk; add lemon peel. Cook and stir until thickened and bubbly. Gradually add provolone, stirring until melted. Gently fold in cooked pasta mixture, asparagus, tuna, and olives. Transfer mixture to a 3-quart baking dish.

For topping, in a small bowl heat the remaining butter over medium heat until melted. Stir in bread crumbs and Parmesan cheese. Sprinkle on top of tuna mixture. Bake for 25 to 30 minutes or until tuna mixture is heated through and topping is golden.