How to turn a function with a for loop into a recursive function

Hello, I have a task to write a recursive function, that solves a system with an upper-triangular coefficient matrix. I mean, to solve the system: Ax=b, when A is an upper-triangular coefficient matrix

I wrote a function using for loop, howover I don't know how to turn it into a recursive function. Here's my code:

function x=uppermatsolve(M,b);
x=zeros(size(b));
[n,m]=size(M);
x(n,:)=b(n,:)/M(n,n);
for k=n-1:-1:1
    x(k,:)=(b(k,:)-M(k,k+1:n)*x(k+1:n,:))/M(k,k);
end

Any help is greatly appreciated!