Here are your parts
Replacement parts for Whirlpool RBD305PDQ11 ELECTRIC OVEN | AppliancePartsPros.com

See the attachment for the tech sheet.

First check the power to the unit.
Try flipping the breaker off/on slowly a couple times, sometimes you can loose half the line without actually tripping the breaker.
If this does nothing, check the voltage at the plug
L1 to L2 should be 240 volts
L1 to Neutral and L2 to Neutral, both should be 120 volts.
If OK
Unplug the unit and check the wires at the terminal strip in the machine to make sure none are loose or burned out
If OK
Check the power at the terminal strip.
[COLOR="Red"]Be careful as 240 volts is lethal !!![/COLOR]

Next check the thermal fuse (upper left in the wiring diagram).
This kills power to the transformer (Item 5 in Section 5 of the parts).
I cannot find it in the parts so you will have to call AppliancePartsPros.

Often they look like the following and are in the harness close to the control board or by the transformer.
Part number: AP3110028