Can I charge a DC 5V - 2.15 A power bank with an Apple Macbook charger?
Yes, that is entirely possible. The power bank accepts standard USB power, and the MacBook charger with USB-C will be just that when you add the USB-C to micro-USB cable.

Note ofcourse that it won't charge faster than the standard charger. Even though the MacBook charger is a 29W charger, it won't charge your power bank at the full rate (instead it will charge at somewhere between 2.6W and 7.8W - most probably at 4.68W).