Grilled Tofu Quesadillas

1 package tofu
1 package flour tortillas
2 medium onions, sliced thin
Monterey jack cheese, shredded
2 tomatoes, thinly sliced
Guacamole (for garnish)
Salsa (for garnish)

Grill tofu on a barbecue grill or in a skillet until brown and crisp. Slice into thin pieces. Saut