Enjoy this mayo in deviled eggs, smoked salmon with capers, or a cold meat mini sandwich hors d'oeuvre.
Combine olive and safflower oils in a large glass measuring cup. Place egg, mustard, and salt in the bowl of a food processor fitted with the plastic blade. Process until mixture is foamy and pale, about 1 1/2 minutes. With the machine running, add oil mixture through the feed tube, a drop at a time, until mixture starts to thicken (about 1/4 cup oil); continue processing a few minutes to completely emulsify. Add remaining oil mixture in a slow, steady stream, and process until fully incorporated. Slowly add lemon juice and zest, and process just until combined. Season with additional salt, if desired. Store in an airtight container in the refrigerator up to 5 days.