Can I Apply to Stanford Restrictive Early Action and Northwestern Early Decision in the Same Application Cycle?

No.

You could apply Stanford REA and Northwestern Regular Decision. Stanford REA is nonbinding, and its restrictions do allow regular-decision applications elsewhere.

To apply Northwestern ED, you would need to forgo Stanford REA and apply to Stanford in the Regular Decision round instead. Because Northwestern ED is binding, choose that route only if Northwestern is clearly your first choice and the financial aid estimate makes attendance workable. Stanford REA can be a sensible option when Stanford is your leading preference but you want to keep all regular-decision choices open.