Sautee the onions and peppers for about 5 minutes. Add the corn, cumin, and green pepper hot sauce. Salt and pepper, or season to taste. Add a can of drained Cannellini beans.
To make the guacamole, mix the mashed avocado, sour cream, onions, and lime. Add the green hot sauce (to taste) and salt.
Layer on top of the prepared tostada shell a thick layer of guacamole. Spoon the bean and pepper mixture on top, adding lettuce, cheese, and tomatoes.
Drizzle with more green pepper hot sauce if desired.