NDX underperformance vs. SPX is becoming extreme here, last time (in June 2022 right after the OPEX Quadruple witching we bounced massively on it until mid July
This chart is the Weekly (log term) showing an intact uptrend right at the bottom of it here.
Bottom Line buy here NDX hedged in SPX you are being supported by L/T Moving average below. 200d-MA
Since SPX and NDX moves closer the Historical Volatility 8% (your risk) in entering the spread has a lower than the mrket currenlty at 27%.