For anyone having the same problem, below there's the fixed code for IFFT. I'm having some issues on dividing by N inside the recursive function, so it is done outside.
P = [%vector of the evaluations];
N = length(P);
y = IFFT(P)/N;
function y = IFFT(P)
% This works only if N = 2^k
N = length(P);
n = N/2;
omega = exp(-2*pi*1i/N);
if N == 1
y = P;
else
P_e = P(1:2:end);
P_o = P(2:2:end);
y_e = IFFT(P_e);
y_o = IFFT(P_o);
y = zeros(N,1);
for j = 1 : n
y(j) = y_e(j) + omega^(j-1)*y_o(j);
y(j+n) = y_e(j) - omega^(j-1)*y_o(j);
end
end
end
