At this frequency you can ASK with a NAND gate. Follow it with a band pass filter to remove the DC level during the off times and also the harmonics of the square wave.
You can copy the topologies used in the early days of MW AM broadcast receivers.
If your received signal is large, use a diode detector (rectifier) followed by a RC low pass filter. This is the basis of the original "crystal sets."
If the received signal is weak, add an RF amplifier before the detector and possibly an amplifier after the detector. This topology is called "tuned RF."