Crustless Smoked Turkey and Spinach Quiche

Cooking spray

cubed smoked turkey ham (such as Jennie-0)

chopped onion

freshly ground black pepper

shredded Swiss cheese, divided

fresh baby spinach leaves

fat-free cottage cheese

evaporated fat-free milk

shredded reduced-fat cheddar cheese

large eggs

large egg whites

all-purpose flour (about 2 1/4 ounces)

baking powder