Is it legal to pay me a base salary and require me to work 50 hours per week?

I work for a pizza franchise and I am the general manager here. I have been doing this job for almost 2 years now. When offered the position I was told that I would be paid a base salary which was great. I needed the increase in pay so it was all good. they require me to work 50 hours a week and if I am below that for any reason they question me on it. I was under the impression from other positions that I held that salary pay is based on 40 hours a week and anything over had to be compensated with time off accumalation or overtime pay. What I do here is run all aspects of the store paperwork, customer service, making the pizzas, hiring/firing, training employees and manageing employees. I am just curious if them requiring me to work 50 hours a week is legal or not. Alot of people I talk to do not believe that it is.