Preheat oven to 375 degrees.
Cut the ends off of the onion, and remove the outer layer. Cut onion into 1/2-inch-wide slices, and separate into rings.
Using a blender or food processor, grind Fiber One to a breadcrumb-like consistency. Pour Fiber One “breadcrumbs” into a small dish and mix in salt, and any optional spices you like.
Next, fill a small bowl (just large enough for onion rings to fit in) with egg substitute. One by one, coat each ring first in egg and then in the “breadcrumbs” (give each ring a shake after the egg bath).
Evenly place rings on a baking dish sprayed with nonstick spray. Cook for 20 to 25 minutes, flipping rings over about halfway through.