Without a model number for your Kenmore 790 gas range, it is difficult to provide accurate troubleshooting help for this problem. Most Kenmore 790 gas ranges have a glow bar igniter system that uses a safety valve. You could have a wiring failure, a bad control/thermostat, a failed igniter or a bad safety gas valve that could be causing this problem. If the range uses a separate burner for the broil and the bake functions then the control or the oven temperature sensor probe would be the suspect components that could have failed. You will normally see an error code on the display if you have a range with an electronic control and the temperature sensor is bad. You will likely need a service technician to diagnose and repair this failure. Here is a link for the Sears Service website:
Sears Home Services
If you want to attempt a do-it-yourself repair, submit additional details and the full model number of your Kenmore 790 range. The model number is often found on the base of the range in front of the right front leveling leg. Open the drawer below the oven to view this area. If you have a slide-in range, open the oven door and look on the side of the opening of the oven cavity to find the model number.