"I jokingly asked if he was good at flying cars." (Terrible example, I know.)

However I'm not 100% certain that 'Jokingly' is even a word. Try:

"In jest, I asked if he was good at flying cars."

Jokingly; adverb: i.e: When I jokingly asked my buddy if he was any good at flying cars, he gunned the motor and showed me how fast his car could fly. Then, seriously, we hit a speed bump and the car was off the ground, flying.

The Yankee Clipper's topmost sails were jokingly referred to as "cloud-cleavers".