Spray a 9x13 baking dish. Cook pasta until about 2 minutes under regular cook time (probably about 5-6 minutes). Drain, add to prepared dish.

Combine evaporated milk, Ranch dressing and pepper in a 3 quart heavy saucepan. Bring it just to a boil then lower heat, stirring frequently until dry ingredients are dissolved. Simmer, uncovered, 25 minutes, stirring frequently. Sauce will thicken slightly.

Layer pasta, chicken, sauce, and cheese into dish. Bake uncovered at 350' for 25 minutes or until hot golden brown and bubbly. Remove lasagna from oven and sprinkle 1/2 cup gluten free bread crumbs on lasagna, return to oven and brown the bread crumbs for 5 minutes.

Sprinkle 1/4 cup green onions before serving.

Let rest 10 minutes before serving.