I think we need additional information to provide useful advice.
1) Can you confirm if the Leaf is one year old with 15K km or if you have had the car for one year and it is older?
2) Do all four brake rotors have rust pitting or only the one you took a picture of? Does the back side of the rotor(s) look the same?
3) How often is the Leaf driven, or conversely how long does it sit parked? Where does it sit when parked: garage, outside, close to the ocean? Do you wash the car regularly?
4) What are your driving conditions: highway driving with minimal brake use or stop-and-go traffic with lots of stopping and starting? More importantly, do you fully engage the (mechanical) brakes regularly?
5) Most importantly, do you feel like the brakes are operating correctly or do you have trouble slowing the car?
As the previous poster noted, disc rotors do get a light coat of superficial rust when sitting, which will be scrubbed off the next time the brakes are engaged. If a car sits for an extended period and/or is parked in more corrosive environments (e.g., next to the ocean) you would expect to see more rust on the rotors.
I would not expect to see rotors with rust pitting on a new car (to me a one year old, 15K km car is new). Without more information about your operating conditions I can only speculate about what's going on, but the pitting suggests that your brake pads are not fully engaging with the outer portion of the rotors. This could be caused by sticky calipers or a misalignment of the pads.
The first thing I would do is really engage the brakes a few times, obviously in a safe location. Get up to road speed and do a controlled emergency stop. Do it a couple more times for fun. Is the entire rotor now clean and shiny (except for the pitting)? If so I would keep monitoring the situation (does the rust come back or get worse?) but probably wouldn't worry about it too much. If not you can ask for more advice here or get your brakes looked at by an expert to make sure all the moving parts are properly lubed and your brakes are functioning correctly.