Crush fiber one bran cereal.

In bowl, mash beans with fork until no whole beans remain. Add crushed cereal, oats, onions and slightly beaten egg; mix well. Shape mixture into 5 patties, each about 3.5 inches in diameter.

Spray 12" skillet with cooking spray. Add patties; cook over medium heat about 10 minutes, turning once, until brown.

For each sandwich, place 1/4 cup spinach leave and one tomato slice on bottom half of bun, top with bean burger.