Hi @michael80321.
Today we no have a simple way to do this, but i created a function that does,
The first print is my result and second is how i did. In my case just to explain i used a compose, but a the utcNow() function get the last day of current month
The function is the below:
"@adddays(concat(add(int(formatDateTime(utcNow(), 'yyyy')),if(equals(formatDateTime(utcNow(), 'MM'), '12'), 1, 0) ),'-',add(int(formatDateTime(utcNow(), 'MM')),if(equals(formatDateTime(utcNow(), 'MM'), '12'), -11, 1) ),'-01T00:00:00Z'),-1)"
I create a idea for do this more simple, please vote on it


I hope i have helped.
Best Regards,
Gustavo Moraes