Severe ringing when high side MOSFET in half bridge circuit switches on

Try probing on the power supply rail. I bet you see those spikes on there. It'll be due to the lead length between your bench supply and the MOSFETs. Clearly you won't see it on the lower FET side because your scope is referenced to that rail but, if you probed back at the power supply I bet you would.

Try a 1uF or 10uF ceramic across the power rails close the MOSFETs.

Assuming that you have dealt to the supply rail bypassing like Andy said and you have slowed up the gate by increasing R1 R7 and doing something to make turn off faster than turn on . If it still rings then there are still two things to try;You can place shottky diodes 60V across DS of the fets and you can place RC snubbers across DS of each FET .